Patent Publication Number: US-10787821-B2

Title: Locking type panel and panel connecting piece and connection method therefor

Description:
FIELDS OF THE INVENTION 
     The present invention relates to a connector for interlocking floor panels, and more particularly, to the floor panels having tongues on the sides thereof, and to the connector having grooves in the sides, the tongues are engaged with the grooves to connect the floor panels. 
     BACKGROUND OF THE INVENTION 
     The interlocking floor panels are used for a long period of time and which are easily connected to each other. The technique is developed further so that the interlocking panels can be used to decorate the wall by connecting the panels to each other and secured on the wall. 
     There are two catalogues for the connection of the floor panels, the first is that the floor panels each have tongue and groove formed on the cooperated sides thereof so that the floor panels can be connected to each other by engaging the tongues with the grooves. The second is to use a connector which is located between the panels so as to connect the floor panels. 
     For the first catalogue, CN 97190692.0 and U.S. Pat. No. 6,874,292 to Unilin Beheer BV disclose the floor panels that have a connection portion composed of a tongue and a groove in the opposite sides thereof, and a mechanical locking device is connected to the connection portion so that the floor panels do not disengaged upwardly from reach other in the direction that is perpendicular to the relative sides, and in the direction that is parallel to the underside of the panels. There are two tools are required when manufacturing the panels and the equipment for manufacturing the panels is required to have higher standard. When assembling the panels, the assemblers have to choose the installation direction and this is an inconvenient requirement for the assemblers. The obvious disadvantage is that, in order to have the tongues and the grooves, a certain width of the material of the board has to be discarded. If the material that is discarded for making the tongues and the grooves reaches 10% of the whole width of the board, this means that 10% of the floor area composed of the panels is disappeared. This also means that the manufacturing cost increases 10%. It is also a waste for the natural source. 
     The second catalogue uses a connector to connect the panels, the connector is made to have symmetrical structure, and the panels have the same structure on the sides to be cooperated with the connector. That is to say, the panels have grooves on the sides, and the connector has tongues on the sides, so that the tongues are engaged with the grooves. China Patent Application No. 200910304656.1 discloses a connector with a tongue on each of two sides thereof, and the tongue has an engaging piece on the top and the bottom thereof. The panels has a groove in each of the sides thereof and each of the grooves has a notch which is shaped to be engaged with the engaging piece. When assembling, the two tongues of the connector are respectively engaged with the grooves of the two connected panels. Theoretically, the connection is by using the connector meets the requirement for connecting the panels. However, it is difficult to make the notch in the groove the same time when forming the groove. The existed equipment cannot make the groove and the notch in one action, wherein the notch is perpendicular to the groove. Besides, after the panels are connected to each other, the locking force in the horizontal direction is made by the flexibility of the material of the connector. If the flexibility of the material of the connector is not strong enough, the locking force in the horizontal direction is not sufficient. If the material for the connector has larger flexibility, when assembling the panels, the assembler has to hammer the other side of the panel to force the connection portions of the panels and the connector to be deformed, so that the connector is connected between the panels. This causes difficulties when assembling and disassembling. Furthermore, the hammering action may damage the groove of the hammered sides of the panels. 
     U.S. Pat. Nos. 6,460,306, 7,614,791 and China Utility Model ZL 02249916.4 306 disclose a similar connector for connecting floor panels, and the connector has two tongues in opposite directions. A base board is connected to the underside of the connector and is connected to the connector by an upright board. The base board has a flange on each of two sides thereof. The panels has a groove in two opposite sides thereof and a positioning slot is defined in the underside of each of the two sides of the panel. The tongues are engaged with the grooves of the panels, and the flanges are engaged with the positioning slots so as to connect the panels. The connection between the tongues and the grooves provides the locking feature in the vertical direction, and the connection between the flanges and the positioning slots provides the locking feature in the horizontal direction, so that the connection between the panels is secure and reliable. However, in order to engage flanges with the positioning slots, the panel has to be tilt so that the side to be connected is positioned to be over the flange so as to be connected with the connector. This is inconvenient for the assemblers because when the long sides of the panels are connected to each other, and the short sides are then to be connected. However, the connected long sides cannot be tilt so that the short side cannot be connected to each other. To improve this problem, the short side can only use a horizontal groove to be connected with each other, and the horizontal groove cannot provide a secure locking feature. 
     U.S. Pat. No. 6,769,217 discloses an interconnecting disengageable flooring system wherein the base board on the underside of the connector does not have the positioning ridge, so that the panels can be horizontally connected to each other. Nevertheless, an engaging slot is required in the base board or the underside of the connector, and the panel has an engaging member in the groove or on the underside thereof. Furthermore, the assembling action has to hammer from the other side of the panels to force the connection portion between the connector and the panel to be deformed slightly, such that the panels can be successfully connected to each other. Again, the similar disadvantages mentioned above are existed. 
     The present invention intends to provide a connector for interlocking floor panels and the floor panels, eliminate the shortcomings mentioned above. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a flooring system and comprises multiple panels connected to each to other. Each panel has a first surface, a second surface which is located corresponding to the first surface and at least three sides. At least two sides of the panel each have a tongue. The panels each have a groove defined in one side thereof, and each groove has an inner side. A top protrusion extends outward from the side having the groove and is located above the groove. Each top protrusion has an end face and a bottom face. The second surface of each panel has a slot defined in the side having the tongue. Each slot has an inside which faces the side having the slot. A tongue is formed between the groove and the slot. Each tongue has a lower protrusion. Each tongue has a tongue top face which faces the groove. Each tongue has a tongue outer face which faces the side having the groove. The tongue outer face does not protrude beyond the end face of the top protrusion. An outer curved face is formed on an outside of the lower protrusion and connected to the tongue outer face. An inner curved face is formed on an inside of the lower protrusion and faces the slot. 
     At least one first stepped portion is formed between the tongue top face and the inner side. Each of the at least one first stepped portion has an engaging face on a top thereof. Each of the at least one first stepped portion has a contact face facing the side having the groove. 
     Preferably, the first stepped portion and a second stepped portion are formed between the tongue top face and the inner side. The first stepped portion has the engaging face on the top thereof and the contact face on the side thereof. The second stepped portion has an engaging face on a top thereof and a contact face on the side thereof. 
     Preferably, the first stepped portion extends from an area between the tongue top face and the inner side of the groove. The first stepped portion has the engaging face on the top thereof. The tongue has a lower protrusion. A top recess is formed between the tongue outer face and the inner curved face of the lower protrusion. A top curved face is connected between an outside of the top recess and the tongue outer face. An outer curved face is connected between an inside of the top recess and the inner curved face. 
     Preferably, the outer curved face of the lower protrusion is a curved face. 
     Preferably, the outer curved face of the lower portion is an curved face. 
     Preferably, the inner curved face of the lower protrusion is a curved face. 
     Preferably, the inner curved face of the lower protrusion is an curved face. 
     Preferably, the tongue has a resilient slot defined in an underside thereof. 
     Preferably, the connector is an elongate connector and has a symmetric top end. The connector has a base board on a lower end thereof. An upright portion extends from the base board. The base board has a bottom face and two side faces. The base board has a locking member on a top of each of the two sides thereof. A locking piece extends laterally from each of two sides of the upright portion. The locking piece has a side face. The upright portion has a top face. An engaging slot is defined between the locking piece of the upright portion and the locking member of the base board. The engaging slot defines a top wall in a bottom of the locking piece. The upright portion has an inside wall formed in each of two sides thereof. The base board has a lower recess defined in a top face of each of two sides thereof. The locking member is located between the lower recess and the side face. The locking member has a wedge-shaped cross section. The lower recess has an curved wall formed at the inside of the locking member. A first ridge extends between the top wall and the inside wall. The first ridge has an engaging face formed at the underside thereof and a contact face formed at a side thereof. 
     Preferably, the first ridge and the second ridge are formed between the top wall and the inside wall. The first ridge has the engaging face formed at the underside thereof and the contact face formed at the side thereof. The second ridge has an engaging face formed at an underside thereof and a contact face formed at a side thereof. 
     Preferably, a top bump is formed between the inside wall and the curved wall of the lower recess. A side curved face is connected between the outside of the top bump and the curved wall. A top curved face is connected between the top of the top bump and the inside wall. 
     Preferably, a notch is defined between the side curved face and the top curved face. 
     Preferably, the upright portion has multiple grooves defined in the top face thereof. 
     Preferably, the top face of the connector has a main groove and a groove is defined in an inner end of the main groove. 
     Preferably, the top face of the connector has a central groove which allows the locking piece to be resiliently deformed. 
     Preferably, the bottom face of the base board has multiple grooves extending along a longitudinal direction of the connector. 
     Preferably, the outside of the locking member has an curved guide face which is located between a top most point of the locking member and the side face. 
     Preferably, the distance between the two side faces of the two locking pieces of the upright portion of the connector is smaller than that between the side faces of the bottom face of the base board. 
     Preferably, a space is defined between the base board of the connector and the upright portion. Another space is defined between the upright portion and the locking piece. 
     Preferably, a curved face is formed between the side face of the locking piece of the connector and the top wall. Another curved face is formed between the engaging face of the first ridge of the connector and the contact face. 
     Preferably, two sides of the side face of the base board of the connector are recessed sides. 
     Preferably, a curved face is formed between the first surface of the panel and the end face. 
     Preferably, a curved face is formed between end face of the top protrusion of the panel and the bottom face. 
     Preferably, a curved face is formed between the engaging face of the first stepped portion of the panel and the contact face. Another curved face is formed between the tongue top face of the tongue of the panel and the tongue outer face. 
     Preferably, a buffering layer is attached to the engaging slot of the connector and the buffering layer is made by a material that is softer than that of the connector. 
     Preferably, the buffering layer is attached on the curved wall, the side curved face, the top curved face, the inside wall, the engaging face and the top wall. 
     Preferably, the buffering layer is attached on the side face of the locking piece. 
     Preferably, the top face of the locking piece of the connector has a buffering plate extending from the center thereof. 
     Preferably, the method for connecting the panels by using the connectors system the following steps: 
     step a: The panel having the tongue are moved toward the connector having the engaging slot on the same plane with the panel. The outer curved face of the tongue of the panel contacts the base board of the connector. 
     step b: The panel are moved and the outer curved face of the tongue of the panel is lifted upward by the base board of the connector. 
     step c: The panel is moved and the lowest point of the lower protrusion of the tongue is moved over the highest point of the locking member of the connector. The lower protrusion of the tongue is moved into the lower recess of the engaging slot of the connector. 
     step d: The panel is moved and the tongue outer face of the tongues contacts the contact face of the first ridge of the connector until the panel is not able to move further. The lower protrusion of the tongue is located within the lower recess of the engaging slot of the connector. The inner curved face of the lower protrusion of the tongue contacts the curved wall of the lower recess of the connector. 
     step e: The side of the first surface of the panel that is lifted up is pressed toward the second surface so as to engage the tongue of the panel with the engaging slot of the connector. 
     The panels of the present invention does not need to be lift up so that the same tongue can be installed to the long side and the short side of the panel, and the same groove can be defined in the long side and the short side of the panel. In other words, the manufacturers need only one blade/tool to make the groove in the long side and the short side of the panel. The connector is extruded as long as the shape of the connector is formed correspondent to the groove of the panel. The connector can be made by engineering plastic, polymer material, wood and metal alloy. The connector is extruded and cut into pieces as desired. The panels of the present invention can be assembled to show different patterns and arrangements. The engagement of the tongues and the grooves are made by pressing the panels so that no hammering action is needed to one side of the panels, so that the panels are not damaged by hammering. 
     The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional view of the connector of the present invention; 
         FIG. 2  is a perspective view to show the connector of the present invention; 
         FIGS. 3, 4, 5, 6, 8  are cross sectional views to show the actions to connect the panels by the connector; 
         FIG. 7  is an enlarged view of the circled portion in  FIG. 6 ; 
         FIGS. 9, 10, 11, 12, 14  are cross sectional views to show the actions to connect the panels by the connector of the second embodiment of the present invention; 
         FIG. 13  is an enlarged view of the circled portion in  FIG. 12 ; 
         FIG. 15  is an end cross sectional view to show another embodiment based on the second embodiment of the present invention; 
         FIG. 16  is an enlarged view of the circled portion in  FIG. 15 ; 
         FIG. 17  shows the bottom of the panel in  FIGS. 15 and 16 ; 
         FIG. 18  is the end cross sectional view of the third embodiment of the panel of the present invention; 
         FIG. 19  is the end cross sectional view of the third embodiment of the connector of the present invention; 
         FIGS. 20, 21, 22, 23, 25  are cross sectional views to show the actions to connect the panels by the connector of the third embodiment of the present invention; 
         FIG. 24  is an enlarged view of the circled portion in  FIG. 23 ; 
         FIG. 26  is an end cross sectional view to show another embodiment based on the third embodiment of the present invention; 
         FIG. 27  is a perspective view to show the embodiment in  FIG. 26 ; 
         FIGS. 28 to 30  are perspective view to show the connection of the third embodiment of the panels and the connector of the present invention; 
         FIG. 31  is the end cross sectional view of the fourth embodiment of the connector of the present invention; 
         FIGS. 32 to 36 and 38  are cross sectional views to show the actions to connect the panels by the connector of the fourth embodiment of the present invention; 
         FIG. 37  is an enlarged view of the circled portion in  FIG. 36 ; 
         FIG. 39  is an end cross sectional view to show another embodiment of the connector based on the fourth embodiment of the present invention; 
         FIG. 40  is an end cross sectional view to show yet another embodiment of the connector based on the fourth embodiment of the present invention; 
         FIG. 41  is an end cross sectional view to show a further embodiment of the connector based on the fourth embodiment of the present invention; 
         FIG. 42  is a cross sectional view of the fifth embodiment of the connector of the present invention; 
         FIG. 43  is an end cross sectional view of the fifth embodiment of the panel of the present invention; 
         FIGS. 44 to 48  are cross sectional views to show the actions to connect the panels by the connector of the fifth embodiment of the present invention; 
         FIG. 49  is an end cross sectional view to show another embodiment of the connector based on the fifth embodiment of the present invention; 
         FIGS. 50 to 53 and 55  are cross sectional views to show the actions to connect the panels by the connector of the embodiment in  FIG. 49 ; 
         FIG. 54  is an enlarged view of the circled portion in  FIG. 53 ; 
         FIG. 56  is an end cross sectional view of the sixth embodiment of the connector of the present invention; 
         FIGS. 57 to 61  are cross sectional views to show the actions to connect the panels by the connector of the sixth embodiment of the present invention; 
         FIG. 62  is a perspective view to show the sixth embodiment of the connector of the present invention; 
         FIG. 63  shows the connector of the sixth embodiment of the present invention is secured by nails; 
         FIG. 64  is an end cross sectional view of the seventh embodiment of the connector of the present invention; 
         FIG. 65  is an end cross sectional view to show another embodiment of the connector based on the seventh embodiment of the present invention; 
         FIG. 66  is an end cross sectional view of the eighth embodiment of the connector of the present invention; 
         FIG. 67  is an end cross sectional view of the ninth embodiment of the connector of the present invention; 
         FIG. 68  is an end cross sectional view to show another embodiment of the connector based on the ninth embodiment of the present invention; 
         FIG. 69  is an end cross sectional view to show yet another embodiment of the connector based on the ninth embodiment of the present invention; 
         FIG. 70  is a perspective view of the tenth embodiment of the panel of the present invention; 
         FIG. 71  show the panels and the connectors of the tenth embodiment of the present invention; 
         FIG. 72  shows the finished combination of the panels and connectors of the tenth embodiment in  FIG. 70  of the present invention; 
         FIG. 73  show three panels are to be connected to each other; 
         FIG. 74  is an enlarged view of the circled portion in  FIG. 73 ; 
         FIG. 75  shows multiple elongate panels are connected longitudinally to each other; 
         FIG. 76  shows that four unit composed of four elongate panels are connected to each other to form a square combination, and 
         FIG. 77  shows that multiple panels are connected to each other to form a transverse S shape combination. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 to 2 , the first embodiment of the connector  20  for connecting the panels  10  of the present invention is an elongate connector  20  which is an inverted T-shaped connected when viewed from either end thereof. The left portion and the right portion of the connector  20  are symmetric to each other. The connector  20  comprises a base board  21  on the lower end thereof, and an upright portion  22  extends from the base board  21 . The base board  21  has a bottom face  210  and two side faces  211 . The base board  21  of the connector  20  has a locking member  23  on the top of each of the two sides thereof. A locking piece  24  extends laterally from each of two sides of the upright portion  22 . The locking pieces  24  each have a side face  240 . The upright portion  22  has a top face  220 , in this embodiment, there are two grooves  221  defined in the top face  220 , and another groove  222  is located between the two grooves  221 , wherein the two grooves  221  is deeper than the groove  222 . An engaging slot  40  is defined between the locking piece  24  of the upright portion  22  and the locking member  23  of the base board  21 . The engaging slot  40  defines a top wall  41  in the bottom of the locking piece  24 . The upright portion  22  has an inside wall  42  formed in each of two sides thereof. The base board  21  has a lower recess  400  defined in the top face of each of two sides thereof. The locking member  23  is located between the lower recess  400  and the side face  211 . The locking member  23  has a wedge-shaped cross section. The lower recess  400  has a curved wall  410  formed at the inside thereof and facing the locking member  23 . 
     Three grooves  212  are defined along the longitudinal direction in the bottom face  210  of the base board  21 . 
       FIG. 3  shows the panel  10  of the present invention and comprises a first surface and a second surface which is located corresponding to the first surface. At least two of the three sides of the panel  10  each have a tongue  30 . Only one side of the two panels  10  are shown for convenience of description of the connection between the connector  20  and the panels  10 . The panel  10  has a groove  33  defined in the side having the tongue  30 , the groove  33  has an inner side  330 . A top protrusion  70  extends outward from the side having the groove  33 . The top protrusion  70  has an end face  701  and a bottom face  702 . The second surface of each panel  10  has a slot  72  defined in one side thereof. The slot  72  has an inside  721  which faces the side having the slot  72 . A tongue  30  is formed between the groove  33  and the slot  72 . The tongue  30  has a lower protrusion  300 . The tongue  30  has a tongue top face  31  which faces the groove  33 , and the tongue  30  has a tongue outer face  32  which faces the side having the groove  33 . The tongue outer face  32  does not protrude beyond the end face  701  of the top protrusion  70  so that the surface of the panel  10  is not affected and the material for the panel  10  not wasted. A first stepped portion  34  is formed between the tongue top face  31  and the inner side  330 . The first stepped portion  34  has an engaging face  341  on the top thereof. The first stepped portion  34  has a contact face  342  which faces the side of the panel  10 . The tongue  30  is engaged with the engaging slot  40  of the connector  20 . The tongue  30  has a lower protrusion  300  for being received in the engaging slot  40  of the connector  20 . The lower protrusion  300  of the tongue  30  is engaged with the lower recess  400  of the connector  20 . As shown in  FIG. 4 , an outer curved face  301  is formed between the outside of the lower protrusion  300  and the tongue outer face  32 . An inner curved face  302  is formed on the inside of the lower protrusion  300  and faces the slot  72 . 
     In this embodiment, the outer curved face  301  and the inner curved face  302  are both a curved face. 
       FIG. 1  shows that the distance between the side faces  240  of the two locking pieces  24  of the upright portion  22  of the connector  20  is smaller than that between the side faces  211  of the base board  21 . 
     An inclined guide face  420  is formed on the outside of the locking member  23  and located between the highest point of the locking member  23  and the side face  211  of the base board  21 . 
     As shown in  FIGS. 3 to 6, and 8 , the assembling actions of the first embodiment of the present invention are disclosed.  FIG. 3  shows that the panel  10  on the left is connected to the connector  20 , and the panel  10  on the right having the tongue  30  is moved toward the connector  20  with the engaging slot  40  on the same plane with the panel  10 . 
     When the panel  10  contacts the connector  20  on the same plane, the outer curved face  301  of the tongue  30  contacts the guide face  420  of the locking member  23  of the engaging slot  40 . 
     When the panel  10  contacts the connector  20  on the same plane, the at least one side of the contact position is an inclined face or a curved face, so that the curved face guides the panel  10  to change its height relative to the side of the connector  20 .  FIG. 3  shows that the panel  10  having the tongue  30  on the right is guided by the curved face and lifted up. 
     When the panel  10  having the tongue  30  is moved toward the connector  20  having the engaging slot  40 , the outer curved face  301  of the tongue  30  contacts the guide face  420  of the locking member  23  of the engaging slot  40  to lift the panel  10 . 
     When the lowest point of the lower protrusion  300  of the panel  10  having the tongue  30  moves to the highest point of the locking member  23  of the connector  20  having the engaging slot  40 , as shown in  FIG. 4 , the panel  10  cannot be lifted up anymore. 
     The horizontal distance L 1  between a vertical extension line of the lowest point of the lower protrusion  300  of the tongue  30  of the panel  10  and a vertical extension line of the highest point of the tongue outer face  32  of the lower protrusion  300  is smaller than the horizontal distance L 2  between a vertical extension line of the highest point of the locking member  23  of the connector  20  and a vertical extension line of the lowest point of the side face  240 . As shown in  FIG. 4 , L 1 &lt;L 2 . 
     When the panel  10  having the tongue  30  is continuously moved toward the connector  20  having the engaging slot  40 , the lower protrusion  300  of the tongue  30  is moved into the lower recess  400  of the engaging slot  40  of the connector  20 . The inner curved face  302  of the lower protrusion  300  of the tongue  30  contacts the curved wall  410  of the lower recess  400  of the connector  20 . The contact face  342  of the first stepped portion  34  of the tongue  30  contacts the side face  240  of the connector  20  as shown in  FIG. 5 , so that the panel  10  with the tongue  30  cannot be moved toward the connector  20  having the engaging slot  40  on the same plane. Because of L 1 &lt;L 2 , during the process of moving the panel  10  having the tongue  30  toward the connector  20  having the engaging slot  40 , when the contact face  342  of the first stepped portion  34  of the tongue  30  contacts the side face  240  of the connector  20 , the lower protrusion  300  of the tongue  30  is moved into the lower recess  400  of the engaging slot  40  of the connector  20 . Therefore, the connection between the panels  10  and the connector  20  can be completed by pressing the panel  10 . 
       FIG. 5  is used to describe the steps for moving the panels  10  toward the connector  20 . The panel  10  on the right is moved downward a little bit due to the gravity to allow the inner curved face  302  of the lower protrusion  300  of the tongue  30  to contact the curved wall  410  of the lower recess  400  of the connector  20 . Before that the contact face  342  of the first stepped portion  34  of the tongue  30  of the panel  10  contacts the side face  240  of the connector  20 , the panel  10  contacts the connector  20  by the curved face which makes the movement of the panel  10  be easy without using any tool to force the panel  10  to move. 
     The horizontal distance L 3  between a vertical extension line of the lowest point of the lower protrusion  300  of the tongue  30  of the panel  10  and a vertical extension line of the contact face  342  of the first stepped portion  34  of the tongue  30  is larger than the horizontal distance L 4  between a vertical extension line of the lowest point of the curved wall  410  of the engaging slot  40  and a vertical extension line of the lowest point of the side face  240 . As shown in  FIG. 5 , L 3 &gt;L 4 . 
     When the panel  10  having the tongue  30  is continuously moved toward the connector  20  having the engaging slot  40 , and the contact face  342  of the first stepped portion  34  of the tongue  30  is in contact with the side face  240  of the panel  20 , the lower protrusion  300  of the tongue  30  is moved into the lower recess  400  of the engaging slot  40  of the connector  20  as shown in  FIG. 5 . Because of L 3 &gt;L 4 , the lowest point of the lower protrusion  300  of the tongue  30  is not yet in contact with the lowest point of the curved wall  410  of the engaging slot  40  of the connector  20 . Therefore, the connection between the panels  10  and the connector  20  can be completed by pressing the panel  10 . 
     The horizontal distance L 5  between a vertical extension line of the outside of the contact face  342  of the first stepped portion  34  and the vertical line of the inner side  330  of the panel  10  is smaller than the horizontal distance L 6  between a vertical extension line of an outside of the side face  240  and the vertical line of the highest point of the inside wall  42  of the engaging slot  42 . As shown in  FIG. 6 , L 5 &lt;L 6 . 
     By pressing the lifted portion of the panel  10  at the contact portion between the panel  10  and the connector  20  as shown by the arrow head in  FIGS. 6 and 7 , the contact face  32  of the first stepped portion  34  contacts the side face of the connector, so that the panel  10  and the connector  20  cannot be moved toward on the same plane. The inner curved face  302  of the lower protrusion  300  of the tongue  30  pushes the curved wall  410  of the engaging slot  40  to deform the material below the engaging slot  40  such that the tongue  30  is able to move downward and into the engaging slot  40 . 
     As shown in  FIG. 6 , when the panel  10  with the tongue  30  is pressed downward, the material below the engaging slot  40  is deformed which is shown by the dotted line and the solid line in  FIG. 7 . When the material below the engaging slot  40  is deformed to allow the tongue  30  to move downward relative to the engaging slot  40 , the contact face  342  of the first stepped portion  40  is offset from the side face  240  of the connector  20 , the lower protrusion  300  of the tongue  30  is engaged with the lower recess  400  of the engaging slot  40  by the guidance of the inner curved face  302  of the lower protrusion  300  and the curved wall  410  of the engaging slot  40 . The locking member  23  is locked in the slot  72 . The material below the engaging slot  40  bounces back by the natural flexibility thereof, the tongue top face  31  of the tongue  30  contacts the underside of the top wall  41  of the engaging slot  40 . The tongue  30  is then engaged with the engaging slot  40  so that the panel  10  does not disengaged from the connector  20  as shown in  FIG. 8 . 
     The locking member  23  is locked in the slot  72 , and the inner curved face  302  of the lower protrusion  300  of the tongue  30  contacts the curved wall  410  of the engaging slot  40 , the tongue  30  is engaged with the engaging slot  40  because that the material below the engaging slot  40  is deformed. After the tongue  30  is engaged with the engaging slot  40 , the material below the engaging slot  40  returns to its initial status, the distance between the outside of the contact face  342  of the first stepped portion  34  and any point of the contact area between the curved wall  410  and the inner curved face  302  is larger than the distance between the intersection point between the side face  240  of the top wall  41  and the side face  240  to the correspondent contact portion of the curved wall  410 . The tongue  30  of the first embodiment cannot be engaged with the engaging slot  40  if the material below the engaging slot  40  is not deformed, so that the panel  10  is securely connected with the connector  20 . 
     As shown in  FIGS. 3 to 6 and 8 , the tongue  30  of the panel  10  is engaged with the engaging slot  40  of the connector  20  by pressing the panel  10 . The assembler does not need to apply a huge force from the other side of the panel  10  so that the other side of the panel  10  is not damaged. 
     The first embodiment of the present invention uses the pressing force to deform the material below the engaging slot  40  to let the inner curved face  302  of the tongue  30  and the curved wall  410  of the engaging slot  40  to guide the tongue  30  to be engaged with the engaging slot  40 . The assembler can either press the panel by hands or feet along the direction shown in  FIGS. 6 and 7  to complete the engagement. 
     For the second embodiment of the present invention, referring to  FIG. 9 , the connector  20 A for connecting the panels  10 A of the present invention is an elongate connector  20 A comprises a base board  21 A on the lower end thereof, and an upright portion  22 A extends from the base board  21 A. The base board  21 A has a bottom face  210 A and two side faces  211 A. The base board  21 A of the connector  20 A has a locking member  23 A on the top of each of the two sides thereof. A locking piece  24 A extends laterally from each of two sides of the upright portion  22 A. The locking pieces  24 A each have a side face  240 A. The upright portion  22 A has a top face  220 A. In this embodiment, there are two grooves  221 A defined in the top face  220 A. An engaging slot  40 A is defined between the locking piece  24 A of the upright portion  22 A and the locking member  23 A of the base board  21 A. The engaging slot  40 A defines a top wall  41 A in the bottom of the locking piece  24 A. The upright portion  22 A has an inside wall  42 A formed in each of two sides thereof. The base board  21 A has a lower recess  400 A defined in the top face of each of two sides thereof. The locking member  23 A is located between the lower recess  400 A and the side face  211 A. The locking member  23 A has a wedge-shaped cross section. The lower recess  400 A has a curved wall  410 A formed at the inside thereof and facing the locking member  23 A. A first ridge  43 A extends between the top wall  41 A and the inside wall  42 A, the first ridge  43 A has an engaging face  431 A at the underside thereof, and a contact face  432 A is formed on a side of the first ridge  43 A. 
       FIG. 10  shows the second embodiment of the panel  10 A of the present invention and comprises a first surface and a second surface which is located corresponding to the first surface. At least two of the three sides each have a tongue  30 A. The panel  10 A has a groove  33 A defined in the side having the tongue  30 A, the groove  33 A has an inner side  330 A. A top protrusion  70 A extends outward from the side having the groove  33 A. The top protrusion  70 A has an end face  701 A and a bottom face  702 A. The second surface of the panel  10  has a slot  72 A defined in one side thereof. The slot  72 A has an inside  721 A which faces the side having the slot  72 A. A tongue  30 A is formed between the groove  33 A and the slot  72 A. The tongue  30 A has a tongue top face  31 A which faces the groove  33 A, and the tongue  30 A has a tongue outer face  32 A which faces the side of the panel  10 A having the groove  33 A. The tongue outer face  32 A does not protrude beyond the end face  701 A of the top protrusion  70 A. The tongue  30 A is engaged with the engaging slot  40 A when the panel  10 A is connected with the connector  20 A. The tongue  30 A has a lower protrusion  300 A which is engaged with the lower recess  400 A of the connector  20 A. An outer curved face  301 A is formed on the outside of the lower protrusion  300 A and the outer curved face  301 A connects the tongue outer face  32 A, An inner curved face  302 A is formed on the inside of the lower protrusion  300 A and faces the slot  72 A. 
     In this embodiment, the outer curved face  301 A and the inner curved face  302 A are both a curved face. 
       FIG. 9  shows that the distance between the side faces  240 A of the two locking pieces  24 A of the upright portion  22 A of the connector  20 A is smaller than that between the side faces  211 A of the base board  21 A. 
     An inclined guide face  420 A is formed on the outside of the locking member  23 A and located between the highest point of the locking member  23 A and the side face  211 A. 
     As shown in  FIGS. 9 to 12, and 14 , the assembling actions of the second embodiment of the present invention are disclosed.  FIG. 9  shows that the panel  10 A on the left is connected to the connector  20 A, and the panel  10 A on the right having the tongue  30 A is moved toward the connector  20 A with the engaging slot  40 A on the same plane with the panel  10 A. 
     When the panel  10 A contacts the connector  20 A on the same plane, the outer inclined face  301 A of the tongue  30 A contacts the guide face  420 A of the locking member  23 A of the engaging slot  40 A of the panel  10 A. 
     When the panel  10 A contacts the connector  20 A on the same plane, the at least one side of the contact position is an inclined face or a curved face, so that the inclined face guides the panel  10 A to change its height relative to the side of the connector  20 A.  FIG. 9  shows that the panel  10 A having the tongue  30 A is guided by the inclined face and lifted up. 
     When the panel  10 A having the tongue  30 A is continuously moved toward the connector  20 A having the engaging slot  40 A, the outer curved face  301 A of the tongue  30 A contacts the guide face  420 A of the locking member  23 A of the engaging slot  40 A to lift the panel  10 A. 
     When the lowest point of the lower protrusion  300 A of the panel  10 A having the tongue  30 A moves to the highest point of the locking member  23 A of the connector  20 A having the engaging slot  40 A, as shown in  FIG. 10 , the panel  10 A cannot be lifted up anymore. 
     The horizontal distance L 1 A between a vertical extension line of the lowest point of the lower protrusion  300 A of the tongue  30 A of the panel  10 A and a vertical extension line of the highest point of the tongue outer face  32 A of the lower protrusion  300 A is smaller than the horizontal distance L 2 A between a vertical extension line of the highest point of the locking member  23 A of the connector  20 A and a vertical extension line of the lowest point of the contact face  432 A of the first ridge  43 A. As shown in  FIG. 10 , L 1 A&lt;L 2 A. 
     When the panel  10 A having the tongue  30 A is continuously moved toward the connector  20 A having the engaging slot  40 A, the lower protrusion  300 A of the tongue  30 A is moved into the lower recess  400 A of the engaging slot  40 A of the connector  20 A. The inner curved face  302 A of the lower protrusion  300 A of the tongue  30 A contacts the curved wall  410 A of the lower recess  400 A of the connector  20 A. The contact face  432 A of the first ridge  43 A of the panel  10 A contacts the tongue outer face  32 A of the tongue  30 A as shown in  FIG. 11 , so that the panel  10 A with the tongue  30 A cannot be moved toward the connector  20 A having the engaging slot  40 A on the same plane. Because of L 1 A&lt;L 2 A, during the process of moving the panel  10 A having the tongue  30 A toward the connector  20 A having the engaging slot  40 A, when the contact face  432 A of the first ridge  43 A of the panel  10 A contacts the tongue outer face  32 A of the tongue  30 A, the lower protrusion  300 A of the tongue  30 A is moved into the lower recess  400 A of the engaging slot  40 A of the connector  20 A. Therefore, the connection between the panels  10 A and the connector  20 A can be completed by pressing the panel  10 . 
       FIG. 11  is used to describe the steps for moving the panels  10 A toward the connector  20 A. The panel  10 A on the right is moved downward a little bit due to the gravity to allow the inner curved face  302 A of the lower protrusion  300 A of the tongue  30 A to contact the curved wall  410 A of the lower recess  400 A of the connector  20 A. Before that the contact face  432 A of the first ridge  43 A of the panel  10 A contacts the tongue outer face  32 A of the tongue  30 A, the panel  10 A contacts the connector  20 A by the curved face which makes the movement of the panel  10 A be easy without using any tool to force the panel  10 A to move. 
     The horizontal distance L 1 A between a vertical extension line of the lowest point of the lower protrusion  300 A of the tongue  30 A of the panel  10 A and a vertical extension line of the highest point of the tongue outer face  32 A of the tongue  30 A is larger than the horizontal distance L 4  between a vertical extension line of the lowest point of the curved wall  410 A of the engaging slot  40 A and a vertical extension line of the lowest point of the contact face  432  of the first ridge  43 A. As shown in  FIG. 11 , L 1 A&gt;L 4 A. 
     When the panel  10 A having the tongue  30 A is continuously moved toward the connector  20 A having the engaging slot  40 A, and the tongue outer face  32 A of the tongue  30 A contacts the contact face  432  of the first ridge  43 A, the lower protrusion  300 A of the tongue  30 A is moved into the lower recess  400 A of the engaging slot  40 A of the connector  20 A as shown in  FIG. 11 . Because of L 1 A&gt;L 4 A, the lowest point of the lower protrusion  300 A of the tongue  30 A is not yet in contact with the lowest point of the curved wall  410 A of the engaging slot  40 A of the connector  20 A. Therefore, the connection between the panels  10 A and the connector  20 A can be completed by pressing the panel  10 A. 
     The horizontal distance L 7 A between a vertical extension line of the inner side  330 A of the panel  10 A and the vertical line of highest point of the tongue outer face  32 A is larger than the horizontal distance L 8 A between a vertical extension line of an outside of the side face  240  of the connector  20 A and the vertical line of the lowest point of the contact wall  432 A of the first ridge  43 A. As shown in  FIG. 12 , L 7 A&gt;L 8 A. 
     By pressing the lifted portion of the panel  10 A at the contact portion between the panel  10 A and the connector  20 A as shown by the arrow head in  FIGS. 11 and 12 , the contact face  32 A of the tongue  30 A contacts the contact face  432 A of the first ridge  43 A, so that the panel  10 A and the connector  20 A cannot be moved toward on the same plane. The inner curved face  302 A of the lower protrusion  300 A of the tongue  30 A pushes the curved wall  410 A of the engaging slot  40 A to deform the material below the engaging slot  40 A such that the tongue  30 A is able to move downward and into the engaging slot  40 A. 
     As shown in  FIG. 12 , when the panel  10 A with the tongue  30 A is pressed downward, the material below the engaging slot  40 A is deformed which is shown by the dotted line and the solid line in  FIG. 13 . When the material below the engaging slot  40 A is deformed to allow the tongue  30 A to move downward relative to the engaging slot  40 A, the tongue outer  32 A of the panel  10 A is offset from the contact face  432 A of the first ridge  43 A of the connector  20 A, the lower protrusion  300 A of the tongue  30 A is engaged with the lower recess  400 A of the engaging slot  40 A by the guidance of the inner curved face  302 A of the lower protrusion  300 A and the curved wall  410 A of the engaging slot  40 A. The locking member  23 A is locked in the slot  72 A. The material below the engaging slot  40 A bounces back by the natural flexibility thereof, the tongue top face  31 A of the tongue  30 A contacts the underside of the engaging face  431 A of the first ridge  43 A. The tongue  30 A is then engaged with the engaging slot  40 A so that the panel  10 A does not disengaged from the connector  20 A as shown in  FIG. 14 . 
     The locking member  23 A is locked in the slot  72 A, and the tongue top face  31 A of the tongue  30 A contacts the engaging face  431 A of the first ridge  43 A. The inner curved face  302 A of the lower protrusion  300 A of the tongue  30 A contacts the curved wall  410 A of the engaging slot  40 A. The tongue  30 A is engaged with the engaging slot  40 A because that the material below the engaging slot  40 A is deformed. After the tongue  30 A is engaged with the engaging slot  40 A, the material below the engaging slot  40 A returns to its initial status, the distance between the outside of the tongue top face  31 A of the tongue  30 A and any point of the contact area between the curved wall  410 A and the inner curved face  302 A is larger than the distance between the intersection point between the engaging face  431 A of the first ridge  43 A of the engaging slot  40 A and the contact face  432 A to the correspondent contact portion of the curved wall  410 A. The tongue  30 A of the second embodiment cannot be engaged with the engaging slot  40 A if the material below the engaging slot  40 A is not deformed, so that the tongue  30 A is securely connected with the engaging slot  40 A. 
     The tongue  30 A of the panel  10 A is engaged with the engaging slot  40 A of the connector  20 A by pressing the panel  10 A. The assembler does not need to apply a huge force to connect the panel  10 A with the connector  20 A, so that no huge force is applied to the other side of the panel  10 A so that the other side of the panel  10 A is not damaged. 
     The second embodiment of the present invention uses the pressing force to deform the material below the engaging slot  40 A to let the inner curved face  302 A of the tongue  30 A and the curved wall  410 A of the engaging slot  40 A to guide the tongue  30 A to be engaged with the engaging slot  40 A. The assembler can either press the panel  10 A by hands or feet along the direction shown in  FIGS. 11 and 12  to complete the engagement. 
       FIG. 15  shows another embodiment based on the second embodiment of the present invention, wherein the tongue  30 A′ of the panel  10 A′ has a resilient slot  305 A′ defined in the underside thereof. As shown in  FIG. 16 , the tongue  30 A′ of the panel  10 A′ is moved to the engaging slot  40 A of the connector  20 A, and when pressing the panel  10 A′ to be connected with the connector  20 A, the resilient slot  305 A′ provide a space for deformation of the tongue  30 A′ of the panel  10 A′. Therefore, when the tongue  30 A′ of the panel  10 A′ is engaged with the engaging slot  40 A of the connector  20 A by way pressing, the material below the engaging slot  40 A of the connector  20 A is slightly deformed, the tongue  30 A′ is deformed in the resilient slot  305 A′, so that the tongue  30 A′ of the panel  10 A′ is easily engaged with the engaging slot  40 A of the connector  20 A. 
       FIG. 17  shows the underside of the panel  10 A′ disclosed in  FIGS. 15 and 16 . The tongue  30 A′ is disclosed. 
     For the third embodiment of the present invention, as shown in  FIGS. 18 and 19 , the panel  10 B is similar to the panel  10  in the first embodiment, and the connector  20 B is similar to the connector  20 A in the second embodiment. 
     As shown in  FIG. 18 , the panel  10 B of the present invention comprises a first surface and a second surface which is located corresponding to the first surface. At least two of the three sides of the panel  10 B each have a tongue  30 B. The panel  10 B has a groove  33 B defined in the side having the tongue  30 B, the groove  33 B has an inner side  330 B. A top protrusion  70 B extends outward from the side having the groove  33 B. The top protrusion  70 B has an end face  701 B and a bottom face  702 B. The second surface of the panel  10 B has a slot  72 B defined in one side thereof. The slot  72 B has an inside  721 B which faces the side having the slot  72 B. A tongue  30 B is formed between the groove  33 B and the slot  72 B. The tongue  30 B has a tongue top face  31 B which faces the groove  33 B, and the tongue  30 B has a tongue outer face  32 B which faces the side having the groove  33 B. The tongue outer face  32 B does not protrude beyond the end face  701 B of the top protrusion  70 B. A first stepped portion  34 B is formed between the tongue top face  31 B and the inner side  330 B. The first stepped portion  34 B has an engaging face  341 B on the top thereof. The first stepped portion  34 B has a contact face  342 B which faces the side of the panel  10 B. The tongue  30  has a lower protrusion  300 B. An outer curved face  301 B is formed between the outside of the lower protrusion  300 B and the tongue outer face  32 B. An inner curved face  302 B is formed on the inside of the lower protrusion  300 B and faces the slot  72 B. 
     Each of the outer curved face  301 B and the inner curved face  302 B of the lower protrusion  300 B of the panel  10 B is a curved face. 
       FIG. 19  shows that the connector  20 B for connecting the panels  10 B of the third embodiment of the present invention comprises a base board  21 B and an upright portion  22 B extends from the base board  21 B. The base board  21 B has a bottom face  210 B and two side faces  211 B. The base board  21 B of the connector  20 B has a locking member  23 B on the top of each of the two sides thereof. A locking piece  24 B extends laterally from each of two sides of the upright portion  22 B. The locking pieces  24 B each have a side face  240 B. The upright portion  22 B has a top face  220 B. In this embodiment, there are two grooves  221 B defined in the top face  220 B. A groove  222 B is defined between the two grooves  221 B wherein the two grooves  221 B are deeper than the groove  222 B. An engaging slot  40 B is defined between the locking piece  24 B of the upright portion  22 B and the locking member  23 B of the base board  21 B. The engaging slot  40 B defines a top wall  41 B in the bottom of the locking piece  24 B. The upright portion  22 B has an inside wall  42 B formed in each of two sides thereof. The base board  21 B has a lower recess  400 B defined in the top face of each of two sides thereof. The locking member  23 B is located between the lower recess  400 B and the side face  211 B. The locking member  23 B has a wedge-shaped cross section. The lower recess  400 B has an curved wall  410 B formed at the inside thereof and facing the locking member  23 B. A first ridge  43 B extends between the top wall  41 B and the inside wall  42 B, the first ridge  43 B has an engaging face  431 B at the underside thereof, and a contact face  432 B is formed on a side of the first ridge  43 B. 
       FIG. 19  shows that the distance between the side faces  240 B of the two locking pieces  24 B of the upright portion  22 B of the connector  20 B is smaller than that between the side faces  211 B of the base board  21 B. 
     An inclined guide face  420 B is formed on the outside of the locking member  23 B and located between the highest point of the locking member  23 B and the upright portion  22 B. 
     Two grooves  212 B are defined in the bottom face  210 B of the base board  21 B and located along the longitudinal direction of the panel  20 B. 
     As shown in  FIGS. 20 to 23, and 25 , the assembling actions of the third embodiment of the present invention are disclosed.  FIG. 20  shows that the panel  10 B on the left is connected to the connector  20 B, and the panel  10 B on the right having the tongue  30 B on the right is moved toward the connector  20 B with the engaging slot  40 B on the same plane with the panel  10 B. 
     When the panel  10 B contacts the connector  20 B on the same plane, the outer curved face  301 B of the tongue  30 B contacts the guide face  420 B of the locking member  23 B of the engaging slot  40 B of the connector  20 B. 
     When the panel  10 B contacts the connector  20 B on the same plane, the at least one side of the contact position is an inclined face or a curved face, so that the curved face guides the panel  10 B to change its height relative to the side of the connector  20 B.  FIG. 20  shows that the panel  10 B having the tongue  30 B is guided by the curved face and lifted up. 
     When the panel  10 B having the tongue  30 B is continuously moved toward the connector  20 B having the engaging slot  40 B, the outer curved face  301 B of the tongue  30 B contacts the guide face  420 B of the locking member  23 B of the engaging slot  40 B to lift the panel  10 B. 
     When the lowest point of the lower protrusion  300 B of the panel  10 B having the tongue  30 B moves to the highest point of the locking member  23 B of the connector  20 B having the engaging slot  40 B, as shown in  FIG. 21 , the panel  10 B cannot be lifted up anymore. 
     The horizontal distance L 1 B between a vertical extension line of the lowest point of the lower protrusion  300 B of the tongue  30 B of the panel  10 B and a vertical extension line of the highest point of the tongue outer face  32 B of the lower protrusion  300 B is smaller than the horizontal distance L 2 B between a vertical extension line of the highest point of the locking member  23 B of the connector  20 B and a vertical extension line of the lowest point of the contact face  432 B of the first ridge  43 B. As shown in  FIG. 22 , L 1 B&lt;L 2 B. 
     When the panel  10 B having the tongue  30 B is continuously moved toward the connector  20 B having the engaging slot  40 B, the lower protrusion  300 B of the tongue  30 B is moved into the lower recess  400 B of the engaging slot  40 B of the connector  20 B. The inner curved face  302 B of the lower protrusion  300 B of the tongue  30 B contacts the curved wall  410 B of the lower recess  400 B of the connector  20 B. The contact face  432 B of the first ridge  43 B of the panel  10 B contacts the tongue outer face  32 B of the tongue  30 B as shown in  FIG. 22 , so that the panel  10 B with the tongue  30 B cannot be moved toward the connector  20 B having the engaging slot  40 B on the same plane. Because of L 1 B&lt;L 2 B, during the process of moving the panel  10 B having the tongue  30 B toward the connector  20 B having the engaging slot  40 B, when the contact face  432 B of the first ridge  43 B of the panel  10 B contacts the tongue outer face  32 B of the tongue  30 B, and the contact face  342 B of the first ridge  34 B contacts the side face  240 B of the locking piece  24 B, the lower protrusion  300 B of the tongue  30 B is moved into the lower recess  400 B of the engaging slot  40 B of the connector  20 B. Therefore, the connection between the panels  10 B and the connector  20 B can be completed by pressing the panel  10 B. 
       FIG. 22  is used to describe the steps for moving the panels  10 B toward the connector  20 B. The panel  10 B on the right is moved downward a little bit due to the gravity to allow the inner curved face  302 B of the lower protrusion  300 B of the tongue  30 B to contact the curved wall  410 B of the lower recess  400 B of the connector  20 B. Before that the contact face  432 B of the first ridge  43 B of the panel  10 B contacts the tongue outer face  32 B of the tongue  30 B, and before the contact face  342 B of the first ridge  34 B contacts the side face  240 B of the locking piece  24 B, the panel  10 B contacts the connector  20 B by the curved face which makes the movement of the panel  10 B be easy without using any tool to force the panel  10 B to move. 
     The horizontal distance L 1 B between a vertical extension line of the lowest point of the lower protrusion  300 B of the tongue  30 B of the panel  10 B and a vertical extension line of the highest point of the tongue outer face  32 B of the tongue  30 B is larger than the horizontal distance L 4 B between a vertical extension line of the lowest point of the curved wall  410 B of the engaging slot  40 B and a vertical extension line of the lowest point of the contact face  432 B of the first ridge  43 B. As shown in  FIG. 22 , L 1 B&gt;L 4 B. 
     When the panel  10 B having the tongue  30 B is continuously moved toward the connector  20 B having the engaging slot  40 B, and the tongue outer face  32 B of the tongue  30 B contacts the contact face  432 B of the first ridge  43 B, the lower protrusion  300 B of the tongue  30 B is moved into the lower recess  400 B of the engaging slot  40 B of the connector  20 B as shown in  FIG. 22 . Because of L 1 B&gt;L 4 B, the lowest point of the lower protrusion  300 B of the tongue  30 B is not yet in contact with the lowest point of the curved wall  410 B of the engaging slot  40 B of the connector  20 B. Therefore, the connection between the panels  10 B and the connector  20 B can be completed by pressing the panel  10 B. 
     The horizontal distance L 5 B between a vertical extension line of the inner side  330 B of the panel  10 B and the vertical line of the outside of the contact face  342 B of the first stepped portion  34 B is smaller than the horizontal distance L 6 B between a vertical extension line of the outside of the side face  240 B of the engaging slot  40 B of the connector  20 B and the vertical line of the highest point of the inside wall  42 B of the engaging slot  40 B. As shown in  FIG. 23 , L 5 B&lt;L 6 B. 
     The horizontal distance L 7 B between a vertical extension line of the inner side  330 B of the panel  10 B and the vertical line of highest point of the tongue outer face  32 B is larger than the horizontal distance L 8 B between a vertical extension line of an outside of the side face  240 B of the connector  20 B and the vertical line of the lowest point of the contact wall  432 B of the first ridge  43 B. As shown in  FIG. 23 , L 7 B&gt;L 8 B. 
     By pressing the lifted portion of the panel  10 B at the contact portion between the panel  10 B and the connector  20 B as shown by the arrow head in  FIG. 23 , the contact face  32 B of the tongue  30 B contacts the contact face  432 B of the first ridge  43 B, and the contact face  342 B of the first stepped portion  34 B contacts the side face  240 B, so that the panel  10 B and the connector  20 B cannot be moved toward on the same plane. The inner curved face  302 B of the lower protrusion  300 B of the tongue  30 B pushes the curved wall  410 B of the engaging slot  40 B to deform the material below the engaging slot  40 B such that the tongue  30 B is able to move downward and into the engaging slot  40 B. 
     As shown in  FIG. 23 , when the panel  10 B with the tongue  30 B is pressed downward, the material below the engaging slot  40 B is deformed which is shown by the dotted line and the solid line in  FIG. 24 . When the material below the engaging slot  40 B is deformed to allow the tongue  30 B to move downward relative to the engaging slot  40 B, the tongue outer  32 B of the tongue  30 B is offset from contact face  432 B of the first ridge  43 B of the engaging slot  40 B, and the contact face  342 B of the first stepped portion  34 B is offset from the side face  240 B, the lower protrusion  300 B of the tongue  30 B is engaged with the lower recess  400 B of the engaging slot  40 B by the guidance of the inner curved face  302 B of the lower protrusion  300 B and the curved wall  410 B of the engaging slot  40 B. The locking member  23 B is locked in the slot  72 B. The material below the engaging slot  40 B bounces back by the natural flexibility thereof, the tongue top face  31 B of the tongue  30 B contacts the underside of the engaging face  431 B of the first ridge  43 B. The engaging face  341 B of the first stepped portion  34 B of the tongue  30 B contacts the underside of the top wall  41 B of the locking piece  24 B of the engaging face  341 B of the first stepped portion  34 B. The tongue  30 B is then engaged with the engaging slot  40 B so that the panel  10 B does not disengaged from the connector  20 B as shown in  FIG. 25 . 
     The tongue top face  31 B of the tongue  30 B contacts the engaging face  431 B of the first ridge  43 B. The engaging face  341 B of the first stepped portion  34 B of the tongue  30 B contacts the top wall  41 B of the locking piece  24 B of the engaging face  341 B of the first stepped portion  34 B. The locking member  23 B is engaged with the slot  72 B. The inner curved face  302 B of the lower protrusion  300 B of the tongue  30 B contacts the curved wall  410 B of the engaging slot  40 B. The tongue  30 B is engaged with the engaging slot  40 B because that the material below the engaging slot  40 B is deformed. After the tongue  30 B is engaged with the engaging slot  40 B, the material below the engaging slot  40 B returns to its initial status, the distance between the outside of the tongue top face  31 B of the tongue  30 B and any point of the contact area between the curved wall  410 B and the inner curved face  302 B is larger than the distance between the intersection point between the engaging face  431 B of the first ridge  43 B of the engaging slot  40 B and the contact face  432 B to the correspondent contact portion of the curved wall  410 B. The tongue  30 B of the second embodiment cannot be engaged with the engaging slot  40 B if the material below the engaging slot  40 B is not deformed, so that the tongue  30 B is securely connected with the engaging slot  40 B. 
       FIG. 26  shows another embodiment based on the third embodiment of the present invention, wherein the connector  20 B is similar to that of the third embedment, and the panel  10 B′ has an curved face connected between the outer curved face  301 B′ of the lower protrusion  300 B′ of the tongue  30 B′ and the inner curved face  302 B′ of the tongue outer face  32 B′. 
       FIG. 27  shows that when the panel  10 B′ is moved toward the connector  20 B the outer curved face  301 B′ contacts the connector  20 B, and the panel  10 B′ is lifted along the guide face  420 B of the locking member  23 B of the connector  20 B. 
       FIGS. 28 to 30  shows the actions to connect the panel  10 B with the connector  20 B, wherein the panel  10 B is connected to the connector  20 B by way of pressing. 
     For the fourth embodiment, the fourth embodiment is a further embedment based on the third embodiment. 
     As shown in  FIG. 31 , the connector  20 C for connecting the panels  10 C of the fourth embodiment of the present invention comprises a base board  21 C and an upright portion  22 C extends from the base board  21 C. The base board  21 C has a bottom face  210 C and two side faces  211 C. The base board  21 C of the connector  20 C has a locking member  23 C on the top of each of the two sides thereof. A locking piece  24 C extends laterally from each of two sides of the upright portion  22 C. The locking pieces  24 C each have a side face  240 C. The upright portion  22 C has a top face  220 C. In this embodiment, there are two grooves  221 C defined in the top face  220 C. A groove  222 C is defined between the two grooves  221 C wherein the two grooves  221 C are deeper than the groove  222 C. An engaging slot  40 C is defined between the locking piece  24 C of the upright portion  22 C and the locking member  23 C of the base board  21 C. The engaging slot  40 C defines a top wall  41 C in the bottom of the locking piece  24 C. The upright portion  22 C has an inside wall  42 C formed in each of two sides thereof. The base board  21 C has a lower recess  400 C defined in the top face of each of two sides thereof. The locking member  23 C is located between the lower recess  400 C and the side face  211 C. The locking member  23 C has a wedge-shaped cross section. The lower recess  400 C has an curved wall  410 C formed at the inside thereof and facing the locking member  23 C. A first ridge  43 B and a second ridge  44 C extend between the top wall  41 C and the inside wall  42 D, the first ridge  43 C has an engaging face  431 C at the underside thereof, and a contact face  432 C is formed on a side of the first ridge  43 C. The second ridge  44 C has an engaging face  441 C at the underside thereof, and a contact face  442 C is formed on a side of the second ridge  44 C. 
     Two grooves  212 C are defined in the bottom face  210 C of the base board  21 C and located along the longitudinal direction of the panel  20 C. 
       FIG. 31  shows that the distance between the side faces  240 C of the two locking pieces  24 C of the upright portion  22 C of the connector  20 C is smaller than that between the side faces  211 C of the base board  21 C. 
     An inclined guide face  420 C is formed on the outside of the locking member  23 C and located between the highest point of the locking member  23 C and the side face  211 C. 
     As shown in  FIGS. 32, 33 , the panel  10 C of the present invention comprises a groove  33 C defined in the side having the tongue  30 C, the groove  33 C has an inner side  330 C. A top protrusion  70 C extends outward from the side having the groove  33 C. The top protrusion  70 C has an end face  701 C and a bottom face  702 C. The second surface of the panel  10 C has a slot  72 C defined in one side thereof. The slot  72 C has an inside  721 C which faces the side having the slot  72 C. A tongue  30 C is formed between the groove  33 C and the slot  72 C. The tongue  30 C has a tongue top face  31 C which faces the groove  33 C, and the tongue  30 C has a tongue outer face  32 C which faces the side having the groove  33 C. The tongue outer face  32 C does not protrude beyond the end face  701 C of the top protrusion  70 C. A first stepped portion  34 C and a second stepped portion  35 C are formed between the tongue top face  31 C and the inner side  330 C. The first stepped portion  34 C has an engaging face  341 C on the top thereof. The first stepped portion  34 C has a contact face  342 C which faces the side of the panel  10 C. The second stepped portion  35 C has an engaging face  351 C on the top thereof. The second stepped portion  35 C has a contact face  352 C which faces the side of the panel  10 C. The tongue  30 C is engaged with the engaging slot  40 C when the panel  10 C is connected to the connector  20 C. The tongue  30 C has a lower protrusion  300 C. An outer curved face  301 C is formed between the outside of the lower protrusion  300 C and the tongue outer face  32 C. An inner curved face  302 C is formed on the inside of the lower protrusion  300 C and faces the slot  72 C. 
     Each of the outer curved face  301 C and the inner curved face  302 C of the lower protrusion  300 C of the panel  10 B of the fourth embodiment is a curved face. 
     As shown in  FIGS. 32 to 36, and 38 , the assembling actions of the fourth embodiment of the present invention are disclosed.  FIG. 32  shows that the panel  10 C on the left is connected to the connector  20 C, and the panel  10 C on the right having the tongue  30 C is moved toward the connector  20 C with the engaging slot  40 C on the same plane with the panel  10 C. 
     When the panel  10 C contacts the connector  20 C on the same plane, the outer curved face  301 C of the tongue  30 C contacts the guide face  420 CB of the locking member  23 C of the engaging slot  40 C of the panel  10 C. 
     When the panel  10 C contacts the connector  20 C on the same plane, the at least one side of the contact position is an inclined face or a curved face, so that the curved face guides the panel  10 C to change its height relative to the side of the connector  20 C.  FIG. 32  shows that the panel  10 C having the tongue  30 C of the fourth embodiment is guided by the curved face and lifted up. 
     When the panel  10 C having the tongue  30 C is continuously moved toward the connector  20 C having the engaging slot  40 C, the outer curved face  301 C of the tongue  30 C contacts the guide face  420 C of the locking member  23 C of the engaging slot  40 C to lift the panel  10 C. 
     When the lowest point of the lower protrusion  300 C of the panel  10 CB having the tongue  30  moves to the highest point of the locking member  23  of the connector  20  having the engaging slot  40 C, as shown in  FIG. 33 , the panel  10 C cannot be lifted up anymore. 
     The horizontal distance L 1 C between a vertical extension line of the lowest point of the lower protrusion  300 C of the tongue  30 C of the panel  10 C and a vertical extension line of the highest point of the tongue outer face  32 C of the lower protrusion  300 C is smaller than the horizontal distance L 2 C between a vertical extension line of the highest point of the locking member  23 C of the connector  20 C and a vertical extension line of the lowest point of the contact face  442 C of the second ridge  44 C. As shown in  FIG. 34 , L 1 C&lt;L 2 C. 
     When the panel  10 C having the tongue  30 C is continuously moved toward the connector  20 C having the engaging slot  40 C, the lower protrusion  300 C of the tongue  30 C is moved into the lower recess  400 C of the engaging slot  40 C of the connector  20 C. The inner curved face  302 C of the lower protrusion  300 C of the tongue  30 C contacts the curved wall  410 C of the lower recess  400 C of the connector  20 C. The contact face  432 C of the first ridge  43 C of the panel  10 C contacts the tongue outer face  32 C of the tongue  30 C. The contact face  442 C of the second ridge  44 C contacts the contact face  342  of the first stepped portion  34 C, and the contact face  352 C of the second stepped portion  35  contacts the side face  240  as shown in  FIG. 35 , so that the panel  10 C with the tongue  30 C cannot be moved toward the connector  20 C having the engaging slot  40 C on the same plane. Because of L 1 C&lt;L 2 C, during the process of moving the panel  10 C having the tongue  30 C toward the connector  20 C having the engaging slot  40 C, when the contact face  432 C of the first ridge  43 C of the panel  10 C contacts the tongue outer face  32 C of the tongue  30 , and the contact face  342 C of the first steeped portion  34 C contacts contact face  442 C of the second ridge  44 C and the contact face  352 C of the second stepped portion  35 C contacts the side face  240 C of the locking piece  24 C, the lower protrusion  300 C of the tongue  30 C is moved into the lower recess  400 C of the engaging slot  40 C of the connector  20 C. Therefore, the connection between the panels  10 C and the connector  20 C can be completed by pressing the panel  10 C. 
       FIGS. 34 and 35  are used to describe the steps for moving the panels  10 C toward the connector  20 C. The panel  10 C on the right is moved downward a little bit due to the gravity to allow the inner curved face  302 C of the lower protrusion  300 C of the tongue  30 C to contact the curved wall  410 C of the lower recess  400 C of the connector  20 C. Before that the contact face  432 C of the first ridge  43 C of the panel  10 C contacts the tongue outer face  32 C of the tongue  30 C and/or the contact face  342 C of the first ridge  34 C contacts contact faced  442 C of the second ridge  44 C and/or the contact face  352 C of the second stepped portion  35 C contacts the side face  240 C of the locking piece  24 C, the panel  10 C contacts the connector  20 C by the curved face which makes the movement of the panel  10 C be easy without using any tool to force the panel  10 C to move. 
     The horizontal distance L 1 C between a vertical extension line of the lowest point of the lower protrusion  300 C of the tongue  30 C of the panel  10 C and a vertical extension line of the highest point of the tongue outer face  32 C of the tongue  30 C is larger than the horizontal distance L 4 C between a vertical extension line of the lowest point of the curved wall  410 C of the engaging slot  40 C and a vertical extension line of the lowest point of the contact face  442  of the second ridge  44 C. As shown in  FIG. 34 , L 1 C&gt;L 4 C. 
     When the panel  10 C having the tongue  30 C is continuously moved toward the connector  20 C having the engaging slot  40 C, and the tongue outer face  32 C of the tongue  30 C contacts the contact face  442 C of the second ridge  44 C, the lower protrusion  300 C of the tongue  30 C is moved into the lower recess  400 C of the engaging slot  40 C of the connector  20 C as shown in  FIG. 34 . Because of L 1 C&gt;L 4 C, the lowest point of the lower protrusion  300 C of the tongue  30 C is not yet in contact with the lowest point of the curved wall  410 C of the engaging slot  40 C of the connector  20 C. Therefore, the connection between the panels  10 C and the connector  20 C can be completed by pressing the panel  10 C. 
     The horizontal distance L 5 C between a vertical extension line of the inner side  330 C of the panel  10 C and the vertical line of the outside of the contact face  342 C of the first stepped portion  34 C is smaller than the horizontal distance L 6 C between a vertical extension line of the outside of the side face  240 C of the engaging slot  40 C of the connector  20 C and the vertical line of the highest point of the inside wall  42 C of the engaging slot  40 C. As shown in  FIG. 35 , L 5 C&lt;L 6 C. 
     The horizontal distance L 7 C between a vertical extension line of the inner side  330 C of the panel  10 C and the vertical line of highest point of the tongue outer face  32 C is larger than the horizontal distance L 8 C between a vertical extension line of an outside of the side face  240 C of the connector  20 C and the vertical line of the lowest point of the contact wall  432 C of the first ridge  43 C. As shown in  FIG. 35 , L 7 C&gt;L 8 C. 
     By pressing the lifted portion of the panel  10 C at the contact portion between the panel  10 C and the connector  20 C as shown by the arrow head in  FIG. 35 , the contact face  32 C of the tongue  30 C contacts the contact face  432 C of the first ridge  43 C, the contact face  342 C of the first stepped portion  34 C contacts the contact face  442 C of the second ridge  44 C, and the contact face  352 C of the second stepped portion  35 C contacts the side face  240   c , so that the panel  10 C and the connector  20 C cannot be moved toward on the same plane. The inner curved face  302 C of the lower protrusion  300 C of the tongue  30 C pushes the curved wall  410 C of the engaging slot  40 C to deform the material below the engaging slot  40 C such that the tongue  30 C is able to move downward and into the engaging slot  40 C. 
     As shown in  FIG. 36 , when the panel  10 C with the tongue  30 C is pressed downward, the material below the engaging slot  40 C is deformed which is shown by the dotted line and the solid line in  FIG. 37 . When the material below the engaging slot  40 C is deformed to allow the tongue  30 C to move downward relative to the engaging slot  40 C, the tongue outer  32 C of the tongue  30 C is offset from contact face  432 C of the first ridge  43 C of the engaging slot  40 C, the contact face  342 C of the first stepped portion  34 C is offset from the contact face  442 C of the second ridge  44 C, and the contact face  352 C of the second stepped portion  35 C is offset from the side face  240 C, the lower protrusion  300 C of the tongue  30 C is engaged with the lower recess  400 C of the engaging slot  40 C by the guidance of the inner curved face  302 C of the lower protrusion  300 C and the curved wall  410 C of the engaging slot  40 C. The locking member  23 C is locked in the slot  72 C. The material below the engaging slot  40 C bounces back by the natural flexibility thereof, the tongue top face  31 C of the tongue  30 C contacts the underside of the engaging face  431 C of the first ridge  43 C. The engaging face  341 C of the first stepped portion  34 C of the tongue  30 C contacts the underside of the engaging face  441  of the second ridge  44 C, and the engaging face  351 C of the second stepped portion  35 C contacts the underside of the top wall  41 C of the engaging slot  40 C. The tongue  30 C is then engaged with the engaging slot  40 C so that the panel  10 C does not disengaged from the connector  20 C as shown in  FIG. 38 . 
       FIGS. 39 to 40  show the alternative embodiment of the connector based on the fourth embodiment, the top face of the connector is different from that of the fourth embodiment. As shown in  FIG. 39 , the top face  220 C′ of the connector  20 C′ has a main groove  223 C′ and a groove  224 C′ is defined in the inner end of the main groove  223 C′. As shown in  FIG. 40 , the top face  220 C″ of the connector  20 C″ has a central groove  225 C″ which allows the locking piece  24 C″ to be resiliently deformed. The top face  220 C″ of the connector  20 C″ in  FIG. 41  is a flat surface. 
     For the fifth embodiment of the present invention, which is based on the third embodiment. 
       FIG. 42  shows that the connector  20 D for connecting the panels  10 D of the third embodiment of the present invention comprises a base board  21 D and an upright portion  22 D extends from the base board  21 D. The base board  21 D has a bottom face  210 D and two side faces  211 D. The base board  21 D of the connector  20 D has a locking member  23 D on the top of each of the two sides thereof. A locking piece  24 D extends laterally from each of two sides of the upright portion  22 D. The locking pieces  24 D each have a side face  240 D. The upright portion  22 D has a top face  220 D. In this embodiment, there are three grooves  221 D defined in the top face  220 D. An engaging slot  40 D is defined between the locking piece  24 D of the upright portion  22 D and the locking member  23 D of the base board  21 D. The engaging slot  40 D defines a top wall  41 D in the bottom of the locking piece  24 D. The upright portion  22 D has an inside wall  42 D formed in each of two sides thereof. The base board  21 D has a lower recess  400 D defined in the top face of each of two sides thereof. The locking member  23 D is located between the lower recess  400 D and the side face  211 D. The locking member  23 D has a wedge-shaped cross section. The lower recess  400 D has an curved wall  410 D formed at the inside thereof and facing the locking member  23 D. A first ridge  43 D extends between the top wall  41 D and the inside wall  42 D, the first ridge  43 D has an engaging face  431 D at the underside thereof, and a contact face  432 D is formed on a side of the first ridge  43 D. A top bump  60 D is formed between the inside wall  42 D and the curved wall  410 D of the lower recess  400 D. A side curved face  601 D is connected between the outside of the top bump  60 D and the curved wall  410 D of the lower recess  400 D. A top curved face  602 D is defined between the top of the top bump  60 D and the inside wall  42 D. 
       FIG. 42  shows that the distance between the side faces  240 D of the two locking pieces  24 D of the upright portion  22 D of the connector  20 D is smaller than that between the side faces  211 D of the base board  21 D. 
     An inclined guide face  420 D is formed on the outside of the locking member  23 D and located between the highest point of the locking member  23 D and the side face  211 D. 
     Three grooves  212 D are defined in the bottom face  210 D of the base board  21 D and located along the longitudinal direction of the panel  20 D. 
     As shown in  FIG. 43 , the panel  10 D of the present invention comprises a groove  33 D defined in the side having the tongue  30 D, the groove  33 D has an inner side  330 D. A top protrusion  70 D extends outward from the side having the groove  33 D. The top protrusion  70 D has an end face  701 D and a bottom face  702 D. The second surface of the panel  10 D has a slot  72 D defined in one side thereof. The slot  72 D has an inside  721 D which faces the side having the slot  72 D. A tongue  30 D is formed between the groove  33 D and the slot  72 D. The tongue  30 D has a tongue top face  31 D which faces the groove  33 D, and the tongue  30 D has a tongue outer face  32 D which faces the side having the groove  33 D. The tongue outer face  32 D does not protrude beyond the end face  701 D of the top protrusion  70 D. The tongue  30 D is engaged with the engaging slot  40 D of the connector  20 D when the panel  10 D is connected to the connector  20 D. The tongue  30 D has a lower protrusion  300 D which is received in the lower recess  400 D of the connector  20 D. An inner curved wall  302 D is formed at the inside of the lower protrusion  300 D and faces the slot  72 D. A first stepped portion  34 D is formed between the tongue top face  31 D and the inner side  330 D. The first stepped portion  34 D has an engaging face  341 D on the top thereof. The first stepped portion  34 D has a contact face  342 D which faces the side of the panel  10 D. A top recess  51 D is formed between the tongue outer face  32 D and the inner curved wall  302 D of the lower protrusion  300 D. A top inclined face  511 D is connected between the outside of the top recess  51 D and the tongue outer face  32 D. An outer inclined face  512 D is connected between the inside of the top recess  51 D and the inner curved wall  302 D. 
     As shown in  FIGS. 44 to 48 , the assembling actions of the fifth embodiment of the present invention are disclosed.  FIG. 44  shows that the panel  10 D on the left is connected to the connector  20 D, and the panel  10 D on the right having the tongue  30 D on the right is moved toward the connector  20 D with the engaging slot  40 D on the same plane with the panel  10 D. 
     When the panel  10 D contacts the connector  20 D on the same plane, the outer inclined face  512 D of the top recess  51 D contacts the guide face  420 D of the locking member  23 D of connector  20 D. 
     When the panel  10 D contacts the connector  20 D on the same plane, the at least one side of the contact position is an inclined face or a curved face, so that the inclined face guides the panel  10 D to change its height relative to the side of the connector  20 D. The panel  10 D having the tongue  30 D is guided by the curved face and lifted up. 
     When the panel  10 D having the tongue  30 D is continuously moved toward the connector  20 D having the engaging slot  40 D, the outer inclined face  512 D of the top recess  51 D of the tongue  30 D contacts the guide face  420 D of the locking member  23 D of the engaging slot  40 D to lift the panel  10 D. 
     When the lowest point of the lower protrusion  300 D of the panel  10 D having the tongue  30 D moves to the highest point of the locking member  23 D of the connector  20 D having the engaging slot  40 D, the panel  10 D cannot be lifted up anymore. 
     The horizontal distance L 1 D between a vertical extension line of the lowest point of the lower protrusion  300 D of the tongue  30 D of the panel  10 D and a vertical extension line of the highest point of the tongue outer face  32 D of the lower protrusion  300 D is smaller than the horizontal distance L 2 D between a vertical extension line of the highest point of the locking member  23 D of the connector  20 D and a vertical extension line of the lowest point of the contact face  432 D of the first ridge  43 D. As shown in  FIG. 45 , L 1 D&lt;L 2 D. 
     When the panel  10 D having the tongue  30 D is continuously moved toward the connector  20 D having the engaging slot  40 D, the lower protrusion  300 D of the tongue  30 D is moved into the lower recess  400 D of the engaging slot  40 D of the connector  20 D. The inner curved face  302 D of the lower protrusion  300 D of the tongue  30 D contacts the curved wall  410 D of the lower recess  400 D of the connector  20 D. The contact face  432 D of the first ridge  43 D of the panel  10 D contacts the tongue outer face  32 D of the tongue  30 D. The contact face  342 D of the first stepped portion  34 D contacts the side face  240 D as shown in  FIG. 45 , so that the panel  10 D with the tongue  30 D cannot be moved toward the connector  20 D having the engaging slot  40 D on the same plane. Because of L 1 D&lt;L 2 D, during the process of moving the panel  10 D having the tongue  30 D toward the connector  20 D having the engaging slot  40 D, when the contact face  432 D of the first ridge  43 D of the panel  10 D contacts the tongue outer face  32 D of the tongue  30 D, and the contact face  342 D of the first ridge  34 D contacts the side face  240 D of the locking piece  24 D, the lower protrusion  300 D of the tongue  30 D is moved into the lower recess  400 D of the engaging slot  40 D of the connector  20 D. Therefore, the connection between the panels  10 D and the connector  20 D can be completed by pressing the panel  10 D. 
       FIG. 45  is used to describe the steps for moving the panels  10 D toward the connector  20 D. The panel  10 D on the right is moved downward a little bit due to the gravity to allow the inner curved face  302 D of the lower protrusion  300 D of the tongue  30 D to contact the curved wall  410 D of the lower recess  400 D of the connector  20 D. Before that the tongue outer face  32 D of the panel  10 D contacts the contact face  432 D of the first ridge  43 D of the connector  20 D, and/or before the contact face  342 D of the first ridge  34 D contacts the side face  240 D of the locking piece  24 D, the panel  10 D contacts the connector  20 D by the curved face which makes the movement of the panel  10 D be easy without using any tool to force the panel  10 D to move. 
     The horizontal distance L 1 D between a vertical extension line of the lowest point of the lower protrusion  300 D of the tongue  30 D of the panel  10 D and a vertical extension line of the highest point of the tongue outer face  32 D of the tongue  30 D is larger than the horizontal distance L 4 D between a vertical extension line of the lowest point of the curved wall  410 D of the engaging slot  40 D and a vertical extension line of the lowest point of the contact face  432 D of the first ridge  43 D. As shown in  FIG. 45 , L 1 B&gt;L 4 B. 
     When the panel  10 D having the tongue  30 D is continuously moved toward the connector  20 D having the engaging slot  40 D, and the tongue outer face  32 D of the tongue  30 D contacts the contact face  432 D of the first ridge  43 D, and/or the contact face  342 D of the first stepped portion  34 D of the panel  10 D contacts the side face  240 D of the connector  20 D, the lower protrusion  300 D of the tongue  30 D is moved into the lower recess  400 D of the engaging slot  40 D of the connector  20 D as shown in  FIG. 46 . Because of L 1 D&gt;L 4 D, the lowest point of the lower protrusion  300 D of the tongue  30 D is not yet in contact with the lowest point of the curved wall  410 D of the top recess  51 D. Therefore, the connection between the panels  10 D and the connector  20 D can be completed by pressing the panel  10 D. 
     The horizontal distance L 5 D between a vertical extension line of the inner side  330 D of the panel  10 D and the vertical line of the outside of the contact face  342 D of the first stepped portion  34 D is smaller than the horizontal distance L 6 D between a vertical extension line of the outside of the side face  240 D of the engaging slot  40 D of the connector  20 D and the vertical line of the highest point of the inside wall  42 D of the engaging slot  40 D. As shown in  FIG. 46 , L 5 D&lt;L 6 D. 
     The horizontal distance L 7 D between a vertical extension line of the inner side  330 D of the panel  10 D and the vertical line of highest point of the tongue outer face  32 D is larger than the horizontal distance L 8 D between a vertical extension line of an outside of the side face  240 D of the connector  20 D and the vertical line of the lowest point of the contact wall  432 D of the first ridge  43 D. As shown in  FIG. 46 , L 7 D&gt;L 8 D. 
     By pressing the lifted portion of the panel  10 D at the contact portion between the panel  10 D and the connector  20 D as shown by the arrow head in  FIG. 46 , the contact face  32 D of the tongue  30 D contacts the contact face  432 D of the first ridge  43 D, and the contact face  342 D of the first stepped portion  34 D contacts the side face  240 D, so that the panel  10 D and the connector  20 D cannot be moved toward on the same plane. The inner curved face  302 D of the lower protrusion  300 D of the tongue  30 D pushes the curved wall  410 D of the engaging slot  40 D to deform the material below the engaging slot  40 D such that the tongue  30 D is able to move downward and into the engaging slot  40 D. 
     As shown in  FIG. 46 , when the panel  10 D with the tongue  30 D is pressed downward, the material below the engaging slot  40 D is deformed which is shown by the dotted line and the solid line in  FIG. 47 . When the material below the engaging slot  40 D is deformed to allow the tongue  30 D to move downward relative to the engaging slot  40 D, the tongue outer  32 D of the tongue  30 D is offset from contact face  432 D of the first ridge  43 D of the engaging slot  40 D, and the contact face  342 D of the first stepped portion  34 D is offset from the side face  240 D, the lower protrusion  300 D of the tongue  30 D is engaged with the lower recess  400 D of the engaging slot  40 D by the guidance of the inner curved face  302 D of the lower protrusion  300 D and the curved wall  410 D of the engaging slot  40 D. The top bump  60 D is engaged with the top recess  51 D of the tongue  30 D. The locking member  23 D is locked in the slot  72 D. The material below the engaging slot  40 D bounces back by the natural flexibility thereof, the tongue top face  31 D of the tongue  30 D contacts the underside of the engaging face  431 D of the first ridge  43 D. The engaging face  341 D of the first stepped portion  34 D of the tongue  30 D contacts the underside of the top wall  41 D of the locking piece  24 D. The tongue  30 D is then engaged with the engaging slot  40 D so that the panel  10 D does not disengaged from the connector  20 D as shown in  FIG. 48 . 
     The tongue top face  31 D of the first stepped portion  34 D contacts the engaging face  431 D of the first ridge  43 D. The engaging face  341 D of the first stepped portion  34 D of the tongue  30 D contacts the top wall  41 D of the locking piece  24 D. The locking member  23 D is engaged with the slot  72 D. The top bump  60 D is engaged with the top recess  51 D of the tongue  30 D. The inner curved face  302 D of the lower protrusion  300 D of the tongue  30 D contacts the curved wall  410 D of the engaging slot  40 D. The tongue  30 D is engaged with the engaging slot  40 D because that the material below the engaging slot  40 D is deformed. After the tongue  30 D is engaged with the engaging slot  40 D, the material below the engaging slot  40 D returns to its initial status, the distance between the outside of the engaging face  341 D of the first stepped portion  34 D and any point of the contact area between the curved wall  410 D and the inner curved face  302 D is larger than the distance between the intersection point between the engaging face  431 D of the first ridge  43 D of the engaging slot  40 D and the contact face  432 D to the correspondent contact portion of the curved wall  410 D. The tongue  30 D of the fifth embodiment cannot be engaged with the engaging slot  40 D if the material below the engaging slot  40 D is not deformed, so that the tongue  30 D is securely connected with the engaging slot  40 D. 
       FIG. 49  shows another embodiment base on the fifth embodiment, wherein the connector  20 D′ of this embodiment is the same as that in the fifth embodiment, and comprises a base board  21 D′ and an upright portion  22 D′ extends from the base board  21 D′. The base board  21 D′ has a bottom face  210 D′ and two side faces  211 D′. The base board  21 D′ of the connector  20 D′ has a locking member  23 D′ on the top of each of the two sides thereof. A locking piece  24 D′ extends laterally from each of two sides of the upright portion  22 D′. The locking pieces  24 D′ each have a side face  240 D′. The upright portion  22 D′ has a top face  220 D′. In this embodiment, there are three grooves  221 D′ defined in the top face  220 D′. An engaging slot  40 D′ is defined between the locking piece  24 D′ of the upright portion  22 D′ and the locking member  23 D′ of the base board  21 D′. The engaging slot  40 D′ defines a top wall  41 D′ in the bottom of the locking piece  24 D′. The upright portion  22 D′ has an inside wall  42 D′ formed in each of two sides thereof. The base board  21 D′ has a lower recess  400 D′ defined in the top face of each of two sides thereof. The locking member  23 D′ is located between the lower recess  400 D′ and the side face  211 D′. The locking member  23 D′ has a wedge-shaped cross section. The lower recess  400 D′ has an curved wall  410 D′ formed at the inside thereof and facing the locking member  23 D′. A first ridge  43 D′ extends between the top wall  41 D′ and the inside wall  42 D′, the first ridge  43 D′ has an engaging face  431 D′ at the underside thereof, and a contact face  432 D′ is formed on a side of the first ridge  43 D′. A top bump  60 D′ is formed between the inside wall  42 D′ and the curved wall  410 D′ of the lower recess  400 D′. A side curved face  601 D′ is connected between the outside of the top bump  60 D′ and the curved wall  410 D′ of the lower recess  400 D′. A top curved face  602 D′ is defined between the top of the top bump  60 D′ and the inside wall  42 D′. 
     The distance between the side faces  240 D′ of the two locking pieces  24 D′ of the upright portion  22 D′ of the connector  20 D′ is smaller than that between the side faces  211 D′ of the base board  21 D′. 
     An inclined guide face  420 D′ is formed on the outside of the locking member  23 D′ and located between the highest point of the locking member  23 D′ and the side face  211 D′ of the base board  21 D′. 
     Three grooves  212 D′ are defined in the bottom face  210 D′ of the base board  21 D′ and located along the longitudinal direction of the panel  20 D′. 
     The side faces  211 D′ of the base board  21 D′ of the connector  20 D′ are two recessed walls which save the use of material and also increase flexibility of the locking member  23 D′ of the base board  21 D′. 
     An inclined face is connected between the side face  240 D′ of the locking piece  24 D′ of the connector  20 D′ and the top face  220 D′. 
     An inclined face is connected between the side face  240 D′ of the locking piece  24 D′ of the connector  20 D′ and the top wall  41 D′. 
     An inclined face is connected between the engaging face  431 D′ of the first ridge  43 D′ of the connector  20 D′ and the contact face  432 D′. 
     The inclined faces mentioned above provide a good transition of the engagement between the panel  10 D′ and the connector  20 D′, so that the connection between the panel  10 D′ and the connector  20 D′ is smooth with less interference. 
     A space  80 D′ is defined between the base board  21 D′ of the connector  20 D′ and the upright portion  22 D′, another space  82 D′ is defined between the upright portion  22 D′ and the locking piece  24 D′. The two spaces  80 D′,  82 D′ save the use of material and make the connector  20 D′ be light in weight. 
     As shown in  FIG. 50  which shows another embodiment based on the fifth embodiment, wherein the panel  10 D′ has a first surface, a second surface located corresponding to the first surface, and a side. The panel  10 D′ comprises a groove  33 D′ defined in the side having the tongue  30 D′, the groove  33 D′ has an inner side  330 D′. A top protrusion  70 D′ extends outward from the side having the groove  33 D′. The top protrusion  70 D′ has an end face  701 D′ and a bottom face  702 D′. The second surface of each panel  10 D′ has a slot  72 D′ defined in one side thereof. The slot  72 D′ has an inside  721 D′ which faces the side having the slot  72 D′. A tongue  30 D′ is formed between the groove  33 D′ and the slot  72 D′. The tongue  30 D′ has a tongue top face  31 D′ which faces the groove  33 D′, and the tongue  30 D′ has a tongue outer face  32 D′ which faces the side having the groove  33 D′. The tongue outer face  32 D′ does not protrude beyond the end face  701 D′ of the top protrusion  70 D′. The tongue  30 D′ is engaged with the engaging slot  40 D′ of the connector  20 D′ when the panel  10 D′ is connected to the connector  20 D′. The tongue  30 D′ has a lower protrusion  300 D′ which is received in the lower recess  400 D′ of the connector  20 D′. An inner curved wall  302 D′ is formed at the inside of the lower protrusion  300 D′ and faces the slot  72 D′. A first stepped portion  34 D′ is formed between the tongue top face  31 D′ and the inner side  330 D′. The first stepped portion  34 D′ has an engaging face  341 D′ on the top thereof. The first stepped portion  34 D′ has a contact face  342 D′ which faces the side of the panel  10 D′. A top recess  51 D′ is formed between the tongue outer face  32 D′ and the inner curved wall  302 D′ of the lower protrusion  300 D′. A top inclined face  511 D′ is connected between the outside of the top recess  51 D′ and the tongue outer face  32 D′. An outer inclined face  512 D′ is connected between the top inclined face  511 D′ and the outer inclined face  512 D′. 
     An inclined face is formed between the first surface of the panel  10 D′ and the end face  701 D′. 
     A curved face is formed between end face  701 D′ of the top protrusion  70 D′ of the panel  10 D′ and the bottom face  702 D′. 
     An inclined face is formed between the engaging face  341 D′ of the first stepped portion  34 D′ of the panel  10 D′ and the contact face  342 D′. 
     Another inclined face is formed between the tongue top face  31 D′ of the tongue  30 D′ of the panel  10 D′ and the tongue outer face  32 D′. 
     The inner curved wall  302 D′ of the lower protrusion  300 D′ is an curved wall. The outer inclined face  512 D′ and the top inclined face  511 D′ each are an inclined face. 
       FIGS. 50 to 53 and 55  is an embodiment based on the fifth embodiment disclosed in  FIG. 49 , the steps for connecting the panels  10 D′ and the connector  20 D′ are the same as those in the fifth embodiment, and will not describe again.  FIG. 54  shows that when the panel  10 D′ having the tongue  30 D′ is pressed downward along the arrow head, the material below the engaging slot  40 D′ is deformed which is shown by the dotted line and the solid line in  FIG. 54 . When the material below the engaging slot  40 D′ is deformed, the tongue  30 D′ to move downward relative to the engaging slot  40 D′, and the tongue outer  32 D′ of the tongue  30 D′ is offset from contact face  432 D′ of the first ridge  43 D′, and the contact face  342 D′ of the first stepped portion  34 D′ is offset from the side face  240 D′, the lower protrusion  300 D′ of the tongue  30 D′ is engaged with the lower recess  400 D′ of the engaging slot  40 D′ by the guidance of the inner curved face  302 D′ of the lower protrusion  300 D′ and the curved wall  410 D′ of the engaging slot  40 D′. The top bump  60 D′ is engaged with the top recess  51 D′ of the tongue  30 D′. The locking member  23 D′ is locked in the slot  72 D′. The material below the engaging slot  40 D′ bounces back by the natural flexibility thereof, the engaging face  341 D of the first stepped portion  34 D′ contacts the underside of the top wall  41 D′ of the locking piece D′. The tongue top face  31 D′ of the tongue  30 D′ of the tongue  30 D contacts the underside of the engaging face  431 D′ of the first ridge  43 D′. The tongue  30 D′ is then engaged with the engaging slot  40 D′ so that the panel  10 D′ does not disengaged from the connector  20 D′ as shown in  FIG. 55 . When the material below the engaging slot  40 D′ is deformed, the tongue  30 D′ to move downward relative to the engaging slot  40 D′, and the tongue outer  32 D′ of the tongue  30 D′ is offset from contact face  432 D′ of the first ridge  43 D′, and the contact face  342 D′ of the first stepped portion  34 D′ is offset from the side face  240 D′, because the inclined face is formed between the engaging face  341 D′ of the first stepped portion  34 D′ of the panel  10 D′ and the contact face  342 D′, the inclined face is formed between the side face  240 D′ of the locking piece  24 D′ of the panel  10 D′ and the top wall  41 D′, the inclined face is formed between the tongue top face  31 D′ of the tongue  30 D′ of the panel  10 D′ and the tongue outer face  32 D′, and the inclined face is formed between the engaging face  431 D′ of the first ridge  43 D′ of the connector  20 D′ and the contact face  432 D′, so that the panel  10 D′ can easily move relative to the connector  20 D′ without interference by the corners. 
       FIG. 55  shows that the two panels  10 D′ are connected to the connector  20 D′. When the two panels  10 D′ are disengaged from the connector  20 D′, the side of the panel  10 D′ that is located remote from the connector  20 D′ is lifted to let the lower protrusion  300 D′ of the tongue  30 D′ push the curved wall  410 D′ to deform the connector  20 D′ as shown in  FIG. 54 . The lower protrusion  300 D′ of the tongue  30 D′ is then disengaged from the lower recess  400 D′ of the connector  20 D′, and the tongue  30 D′ is disengaged from the engaging slot  40 D′. When the side of each of the two panels  10 D′ that is located remote from the connector  20 D′ simultaneously, the top protrusions  70 D′ of the two panels  10 D′ contact each other to form the fulcrum about which the panels  10 D′ are pivoted. At this situation, the inclined face is formed between the first surface of the panel  10 D′ and the end face  701 D′, so that the side of the first surface of the panel  10 D′ is avoided from being damaged when the panel  10 D′ is pivoted. The curved face is formed between the end face  701 D′ of the top protrusion  70 D′ of the panel  10 D′ and the bottom face  702 D′, the curved face avoids the panel  10 D′ from being interfered by the top face  220 D′ of the connector  20 D′ when the panel  10 D′ is pivoted. 
     For the sixth embodiment, the sixth embodiment is based on the third embodiment, wherein the connector  20 E is disclosed in  FIG. 56  and comprises a base board  21 E and an upright portion  22 E extends from the base board  21 E. The base board  21 E has a bottom face  210 E and two side faces  211 E. The base board  21 E of the connector  20 E has a locking member  23 E on the top of each of the two sides thereof. A locking piece  24 E extends laterally from each of two sides of the upright portion  22 E. The locking pieces  24 E each have a side face  240 E. The upright portion  22 E has a top face  220 E. In this embodiment, there are two grooves  221 E defined in the top face  220 E. An engaging slot  40 E is defined between the locking piece  24 E of the upright portion  22 E and the locking member  23 E of the base board  21 E. The engaging slot  40 E defines a top wall  41 E in the bottom of the locking piece  24 E. The upright portion  22 E has an inside wall  42 E formed in each of two sides thereof. The base board  21 E has a lower recess  400 E defined in the top face of each of two sides thereof. The locking member  23 E is located between the lower recess  400 E and the side face  211 E. The locking member  23 E has a wedge-shaped cross section. The lower recess  400 E has an curved wall  410 E formed at the inside thereof and facing the locking member  23 E. A first ridge  43 E extends between the top wall  41 E and the inside wall  42 E, the first ridge  43 E has an engaging face  431 E at the underside thereof, and a contact face  432 E is formed on a side of the first ridge  43 E. A top bump  60 E is formed between the inside wall  42 E and the curved wall  410 E of the lower recess  400 E. A side inclined face  601 E is connected between the outside of the top bump  60 E and the curved wall  410 E of the lower recess  400 E. A top curved face  602 E is defined between the top of the top bump  60 E and the inside wall  42 E. A notch  603 E is formed between the side curved face  601 E and the top curved face  602 E. 
       FIG. 56  shows that the distance between the side faces  240 E of the two locking pieces  24 E of the upright portion  22 E of the connector  20 E is smaller than that between the side faces  211 E of the base board  21 E. 
     An inclined guide face  420 E is formed on the outside of the locking member  23 E and located between the highest point of the locking member  23 E and the side face  211 E. 
     Two grooves  212 E are defined in the bottom face  210 E of the base board  21 E and located along the longitudinal direction of the panel  20 E. 
     The curved wall  410 E of the lower recess  400  that is located close to the inside of the locking member  23  is an curved wall. 
     The notch  603 E between the side inclined face  601 E and the top curved face  602 E properly adjust the force to deform the base board  21 E. 
     As shown in  FIG. 57 , the panel  10 E of sixth embodiment of the present invention comprises a groove  33 E defined in the side having the tongue  30 E, the groove  33 E has an inner side  330 E. A top protrusion  70 E extends outward from the side having the groove  33 E. The top protrusion  70 E has an end face  701 E and a bottom face  702 E. The second surface of the panel  10 E has a slot  72 E defined in one side thereof. The slot  72 E has an inside  721 E which faces the side having the slot  72 E. A tongue  30 E is formed between the groove  33 E and the slot  72 E. The tongue  30 E has a tongue top face  31 E which faces the groove  33 E, and the tongue  30 E has a tongue outer face  32 E which faces the side having the groove  33 E. The tongue outer face  32 E does not protrude beyond the end face  701 E of the top protrusion  70 E. The tongue  30 E is engaged with the engaging slot  40 E of the connector  20 E when the panel  10 E is connected to the connector  20 E. The tongue  30 E has a lower protrusion  300 E which is received in the lower recess  400 E of the connector  20 E. An inner curved wall  302 E is formed at the inside of the lower protrusion  300 E and faces the slot  72 E. A first stepped portion  34 E is formed between the tongue top face  31 E and the inner side  330 E. The first stepped portion  34 E has an engaging face  341 E on the top thereof. The first stepped portion  34 E has a contact face  342 E which faces the side of the panel  10 E. A top recess  51 E is formed between the tongue outer face  32 E and the inner curved wall  302 E of the lower protrusion  300 E. A top inclined face  511 E is connected between the outside of the top recess  51 E and the tongue outer face  32 E. An outer inclined face  512 E is connected between the inside of the top recess  51 E and the inner curved wall  302 E. 
     Each of the inner curved face  302 B of the lower protrusion  300 B of the panel  10 B, the top inclined face  511 E and the outer inclined face  512 E of the top recess  51 E is an inclined face. 
     As shown in  FIGS. 57 to 59, and 61 , the assembling actions of the sixth embodiment of the present invention are disclosed.  FIG. 57  shows that the panel  10 E on the left is connected to the connector  20 E, and the panel  10 E on the right having the tongue  30 E on the right is moved toward the connector  20 E with the engaging slot  40 E on the same plane with the panel  10 E. 
     When the panel  10 B contacts the connector  20 B on the same plane, the outer inclined face  301 B of the tongue  30 B contacts the guide face  420 B of the locking member  23 B of the engaging slot  40 B of the connector  20 B. 
     When the panel  10 E contacts the connector  20 E on the same plane, the lower edge of the tongue  30 E of the panel  10 E contacts the guide face  420 E of the locking member  23 E of the connector  20 E. 
     When the panel  10 E contacts the connector  20 E on the same plane, at least one side of the contact position is an inclined face or a curved face, so that the curved face guides the panel  10 E to change its height relative to the side of the connector  20 E.  FIG. 57  shows that the panel  10 E having the tongue  30 E is guided by the inclined face and lifted up. 
     When the panel  10 E having the tongue  30 E is continuously moved toward the connector  20 E having the engaging slot  40 E, the top inclined face  511 E and the outer inclined face  512 E of the top recess  51 E of the tongue  30 E are cooperated with the guide face  420 E of the locking member  23 E of the tongue  20 E to guide the panel  10 E to be lifted up. 
     When the lowest point of the lower protrusion  300 E of the panel  10 E having the tongue  30 E moves to the highest point of the locking member  23 E of the connector  20 E having the engaging slot  40 E, the panel  10 E cannot be lifted up anymore. 
     The horizontal distance L 1 E between a vertical extension line of the lowest point of the lower protrusion  300 E of the tongue  30 E of the panel  10 E and a vertical extension line of the highest point of the tongue outer face  32 E of the lower tongue  30 E is smaller than the horizontal distance L 2 E between a vertical extension line of the highest point of the locking member  23 E of the connector  20 E and a vertical extension line of the lowest point of the contact face  432 E of the first ridge  43 E. As shown in  FIG. 58 , L 1 E&lt;L 2 E. 
     When the panel  10 E having the tongue  30 E is continuously moved toward the connector  20 E having the engaging slot  40 E, the lower protrusion  300 E of the tongue  30 E is moved into the lower recess  400 E of the engaging slot  40 E of the connector  20 E. The inner curved face  302 E of the lower protrusion  300 E of the tongue  30 E contacts the curved wall  410 E of the lower recess  400 E of the connector  20 E. The contact face  432 E of the first ridge  43 E of the panel  10 E contacts the tongue outer face  32 E of the tongue  30 E, and the contact face  342 E of the first stepped portion  34 E contacts the side face  240 E as shown in  FIG. 58 , so that the panel  10 E with the tongue  30 E cannot be moved toward the connector  20 E having the engaging slot  40 E on the same plane. Because of L 1 E&lt;L 2 E, during the process of moving the panel  10 E having the tongue  30 E toward the connector  20 E having the engaging slot  40 E, when the contact face  432 E of the first ridge  43 E of the panel  10 E contacts the tongue outer face  32 E of the tongue  30 E, and the contact face  342 E of the first ridge  34 E contacts the side face  240 E of the locking piece  24 E, the lower protrusion  300 E of the tongue  30 E is moved into the lower recess  400 E of the engaging slot  40 E of the connector  20 E. Therefore, the connection between the panels  10 E and the connector  20 E can be completed by pressing the panel  10 E. 
       FIG. 58  is used to describe the steps for moving the panels  10 E toward the connector  20 E. The panel  10 E on the right is moved downward a little bit due to the gravity to allow the inner curved face  302 E of the lower protrusion  300 E of the tongue  30 E to contact the curved wall  410 E of the lower recess  400 E of the connector  20 E. Before that the contact face  432 E of the first ridge  43 E of the panel  10 E contacts the tongue outer face  32 E of the tongue  30 E, and/or before the contact face  342 E of the first ridge  34 E contacts the side face  240 E of the locking piece  24 E, the panel  10 E contacts the connector  20 E by the inclined face which makes the movement of the panel  10 E be easy without using any tool to force the panel  10 E to move. 
     The horizontal distance L 1 E between a vertical extension line of the lowest point of the lower protrusion  300 E of the tongue  30 E of the panel  10 E and a vertical extension line of the highest point of the tongue outer face  32 E of the tongue  30 E is larger than the horizontal distance L 4 E between a vertical extension line of the lowest point of the curved wall  410 E of the engaging slot  40 E and a vertical extension line of the lowest point of the contact face  432 E of the first ridge  43 E. As shown in  FIG. 58 , L 1 E&gt;L 4 E. 
     When the panel  10 E having the tongue  30 E is continuously moved toward the connector  20 E having the engaging slot  40 E, and the tongue outer face  32 E of the tongue  30 E contacts the contact face  432 E of the first ridge  43 E, and/or the contact face  342 B of the first stepped portion  34 B of the panel  10 E contacts the side face  240 E of the connector  20 E, the lower protrusion  300 E of the tongue  30 E is moved into the lower recess  400 E of the engaging slot  40 E of the connector  20 E as shown in  FIG. 58 . Because of L 1 E&gt;L 4 E, the lowest point of the lower protrusion  300 E of the tongue  30 E is not yet in contact with the lowest point of the curved wall  410 E of the top recess  51 E. Therefore, the connection between the panels  10 E and the connector  20 E can be completed by pressing the panel  10 E. 
     The horizontal distance L 5 E between a vertical extension line of the inner side  330 E of the panel  10 E and the vertical line of the outside of the contact face  342 E of the first stepped portion  34 E is smaller than the horizontal distance L 6 E between a vertical extension line of the outside of the side face  240 E of the engaging slot  40 E of the connector  20 E and the vertical line of the highest point of the inside wall  42 E of the engaging slot  40 E. As shown in  FIG. 59 , L 5 E&lt;L 6 E. 
     The horizontal distance L 7 E between a vertical extension line of the inner side  330 E of the panel  10 E and the vertical line of highest point of the tongue outer face  32 E is larger than the horizontal distance L 8 E between a vertical extension line of an outside of the side face  240 E of the connector  20 E and the vertical line of the lowest point of the contact wall  432 E of the first ridge  43 E. As shown in  FIG. 59 , L 7 E&gt;L 8 E. 
     By pressing the lifted portion of the panel  10 E at the contact portion between the panel  10 E and the connector  20 E as shown by the arrow head in  FIG. 59 , the contact face  32 E of the tongue  30 E contacts the contact face  432 E of the first ridge  43 E, and the contact face  342 E of the first stepped portion  34 E contacts the side face  240 E, so that the panel  10 E and the connector  20 E cannot be moved toward on the same plane. The inner curved face  302 E of the lower protrusion  300 E of the tongue  30 E pushes the curved wall  410 E of the engaging slot  40 E to deform the material below the engaging slot  40 E such that the tongue  30 E is able to move downward and into the engaging slot  40 E. 
     As shown in  FIG. 59 , when the panel  10 E with the tongue  30 E is pressed downward, the material below the engaging slot  40 E is deformed which is shown by the dotted line and the solid line in  FIG. 60 . When the material below the engaging slot  40 E is deformed to allow the tongue  30 E to move downward relative to the engaging slot  40 E, the tongue outer  32 E of the tongue  30 E is offset from contact face  432 E of the first ridge  43 E of the engaging slot  40 E, and the contact face  342 E of the first stepped portion  34 E is offset from the side face  240 E, the lower protrusion  300 E of the tongue  30 E is engaged with the lower recess  400 E of the engaging slot  40 E by the guidance of the inner curved face  302 E of the lower protrusion  300 E and the curved wall  410 E of the engaging slot  40 E. The top bump  60 E is engaged with the top recess  51 E of the tongue  30 E. The locking member  23 E is locked in the slot  72 E. The material below the engaging slot  40 E bounces back by the natural flexibility thereof, the engaging face  341 E of the first stepped portion  34 E contacts the underside of the top wall  41 E of the locking piece  24 E. The tongue top face  31 E of the tongue  30 E contacts the underside of the engaging face  431 E of the first ridge  43 E. The tongue  30 E is then engaged with the engaging slot  40 E so that the panel  10 E does not disengaged from the connector  20 E as shown in  FIG. 61 . 
     The tongue top face  31 E of the tongue  30 E contacts the engaging face  431 E of the first ridge  43 E. The engaging face  341 E of the first stepped portion  34 E of the tongue  30 E contacts the top wall  41 E of the locking piece  24 E. The locking member  23 E is engaged with the slot  72 E. The inner curved face  302 E of the lower protrusion  300 E of the tongue  30 E contacts the curved wall  410 E of the engaging slot  40 E. The tongue  30 E is engaged with the engaging slot  40 E because that the material below the engaging slot  40 E is deformed. After the tongue  30 E is engaged with the engaging slot  40 E, the material below the engaging slot  40 E returns to its initial status, the distance between the outside of the outside of the engaging face  341 E of the first stepped portion  34 E and any point of the contact area between the curved wall  410 E and the inner curved face  302 E is larger than the distance between the intersection point between the engaging face  431 E of the first ridge  43 E of the engaging slot  40 E and the contact face  432 E to the correspondent contact portion of the curved wall  410 E. The tongue  30 E of the second embodiment cannot be engaged with the engaging slot  40 E if the material below the engaging slot  40 E is not deformed, so that the tongue  30 E is securely connected with the engaging slot  40 E. 
       FIG. 62  shows that holes  604 E are drilled in the top bump  60 E of the connector  20 E as needed, the holes  604 E are drilled at the portions where the notch  603 E is located. When drilling the holes  604 E, the drill is easily guided to the notch  603 E to easily drill the holes  604 E. As shown in  FIG. 63 , the holes  604 E are drilled for securing the connector  10 E. The heads of the nails  90 E are accommodated in the top bump  60 E when the nails  90 E are nailed. 
     For the seventh embodiment, as shown in  FIG. 64 , the connector  20 F for being connected with the panels  10 F is the same as the connector  20 D′ in  FIG. 49 , and the connector  20 F comprises a base board  21 F and an upright portion  22 F extends from the base board  21 F. The base board  21 F has a bottom face  210 F and two side faces  211 F. The base board  21 F of the connector  20 F has a locking member  23 F on the top of each of the two sides thereof. A locking piece  24 F extends laterally from each of two sides of the upright portion  22 F. The locking pieces  24 F each have a side face  240 F. The upright portion  22 F has a top face  220 F. In this embodiment, there are three grooves  221 F defined in the top face  220 F. An engaging slot  40 F is defined between the locking piece  24 F of the upright portion  22 F and the locking member  23 F of the base board  21 F. The engaging slot  40 F defines a top wall  41 F in the bottom of the locking piece  24 F. The upright portion  22 F has an inside wall  42 F formed in each of two sides thereof. The base board  21 F has a lower recess  400 F defined in the top face of each of two sides thereof. The locking member  23 F is located between the lower recess  400 F and the side face  211 F. The locking member  23 F has a wedge-shaped cross section. The lower recess  400 F has an curved wall  410 F formed at the inside thereof and facing the locking member  23 F. A first ridge  43 F extends between the top wall  41 F and the inside wall  42 F, the first ridge  43 F has an engaging face  431 F at the underside thereof, and a contact face  432 F is formed on a side of the first ridge  43 F. A top bump  60 F is formed between the inside wall  42 F and the curved wall  410 F of the lower recess  400 F. A side inclined face  601 F is connected between the outside of the top bump  60 F and the curved wall  410 F of the lower recess  400 F. A top curved face  602 F is defined between the top of the top bump  60 F and the inside wall  42 F. 
     The distance between the side faces  240 F of the two locking pieces  24 F of the upright portion  22 F of the connector  20 F is smaller than that between the side faces  211 F of the base board  21 F. 
     An inclined guide face  420 F is formed on the outside of the locking member  23 F and located between the highest point of the locking member  23 F and the side face  211 F. 
     Three grooves  212 F are defined in the bottom face  210 F of the base board  21 F and located along the longitudinal direction of the panel  20 F. 
     The side faces  211 F of the base board  21 F of the connector  20 F are two recessed walls which save the use of material and also increase flexibility of the locking member  23 F of the base board  21 F. 
     An inclined face is connected between the side face  240 F of the locking piece  24 F of the connector  20 F and the top face  220 F. 
     An inclined face is connected between the side face  240 F of the locking piece  24 F of the connector  20 F and the top wall  41 F. 
     An inclined face is connected between the engaging face  431 F of the first ridge  43 F of the connector  20 F and the contact face  432 F. 
     The connector  20 F is made by plastic and a space  80 F is defined between the base board  21 F of the connector  20 F and the upright portion  22 F, another space  82 F is defined between the upright portion  22 F and the locking piece  24 F. The two spaces  80 F,  82 F save the use of material and make the connector  20 F be light in weight. 
     A buffering layer is attached to the surface of the engaging slot  40 F of the connector  20 F, and the buffering layer is also attached on the surface of each of the curved wall  410 F, the side inclined face  601 F, the top curved face  602 F, the inside wall  42 F, the engaging face  431 F and the top wall  41 F. Besides, the buffering layer is also attached on the surface of the side face  240 F of the locking piece  24 F. The buffering layer is made by the material that is softer than that of the connector  20 F so that the connector  20 F is able to be deformed as desired when the panel  10 F is connected with the connector  20 F. After the panels  10 F are connected with the connector  20 F, the buffering layer provides a buffering feature between the panels  10 F and the connector  20 F to reduce the friction between the panels  10 F and the connector  20 F to solve the problems of shrinking and expanding due to change of temperature or the problems of shifting due to pushing to generate noise. 
     The buffering layer is made by soft material so that the buffering layer can be made with the connector  20 F by way of double-layer extruding. 
       FIG. 65  discloses another embodiment which is based on the seventh embodiment, wherein the connector  20 F′ is the same as the connector  20 F disclosed in the  FIG. 64 , the only difference is that the buffering layer on the surface of the engaging slot  40 F′ is also attached on the surface of each of the curved wall  410 F′, the side inclined face  601 F′, the top curved face  602 F′, the inside wall  42 F′, the engaging face  431 F′, contact face  432 F′, the top wall  41 F′ and the side face  240 F′. Furthermore, the buffering layer is attached on the surface of each of the top face  220 F′ of the upright portion  22 F′ and the groove  221 F′ of the top face  220 F′. 
       FIG. 66  discloses the eighth embodiment, wherein the connector  20 G basically the same as the connector  20 F′ in  FIG. 65 , and comprises a base board  21 G and an upright portion  22 G extends from the base board  21 G. The base board  21 G has a bottom face  210 G and two side faces  211 G. The base board  21 G of the connector  20 G has a locking member  23 G on the top of each of the two sides thereof. A locking piece  24 G extends laterally from each of two sides of the upright portion  22 G. The locking pieces  24 G each have a side face  240 G. The upright portion  22 G has a top face  220 G. In this embodiment, there are two grooves  221 G defined in the top face  220 G. An engaging slot  40 G is defined between the locking piece  24 G of the upright portion  22 G and the locking member  23 G of the base board  21 G. The engaging slot  40 G defines a top wall  41 G in the bottom of the locking piece  24 G. The upright portion  22 G has an inside wall  42 G formed in each of two sides thereof. The base board  21 G has a lower recess  400 G defined in the top face of each of two sides thereof. The locking member  23 G is located between the lower recess  400 G and the side face  211 G. The locking member  23 G has a wedge-shaped cross section. The lower recess  400 G has an curved wall  410 G formed at the inside thereof and facing the locking member  23 G. A first ridge  43 G extends between the top wall  41 G and the inside wall  42 G, the first ridge  43 G has an engaging face  431 G at the underside thereof, and a contact face  432 G is formed on a side of the first ridge  43 G. A top bump  60 G is formed between the inside wall  42 G and the curved wall  410 G of the lower recess  400 G. A side inclined face  601 G is connected between the outside of the top bump  60 G and the curved wall  410 G of the lower recess  400 G. A top curved face  602 G is defined between the top of the top bump  60 G and the inside wall  42 G. 
     The distance between the side faces  240 G of the two locking pieces  24 G of the upright portion  22 G of the connector  20 G is smaller than that between the side faces  211 G of the base board  21 G. 
     An inclined guide face  420 G is formed on the outside of the locking member  23 G and located between the highest point of the locking member  23 G and the side face  211 G. 
     Three grooves  212 G are defined in the bottom face  210 G of the base board  21 G and located along the longitudinal direction of the panel  20 G. 
     The side faces  211 G of the base board  21 G of the connector  20 G are two recessed walls which save the use of material and also increase flexibility of the locking member  23 G of the base board  21 G. 
     An inclined face is connected between the side face  240 G of the locking piece  24 G of the connector  20 G and the top face  220 G. 
     An inclined face is connected between the side face  240 G of the locking piece  24 G of the connector  20 G and the top wall  41 G. 
     An inclined face is connected between the engaging face  431 G of the first ridge  43 G of the connector  20 G and the contact face  432 G. 
     The connector  20 G is made by plastic and a space  80 G is defined between the base board  21 G of the connector  20 G and the upright portion  22 G. The space  80 G saves the use of material and make the connector  20 G be light in weight. 
     The top face  220 G of the upright portion  22 G of the connector  20 G has a central groove  84 G which allows the locking piece  24 G and the first ridge  43 G to be resiliently deformed. The central groove  84 G is designed to increase the flexibility of the locking piece  24 G and the first ridge  43 G, so that when the tongue is engaged with the engaging slot  40 G of the connector  20 G, the material under the engaging slot  40  is deformed, and the locking piece  24 G and the first ridge  43 G are also deformed. This make the connection between the panels and the connector  20 G be easy and convenient. The central groove  84 G also saves the use of material of the connector  20 G to decrease the weight of the connector  20 G. 
     A buffering layer is attached to the surface of the engaging slot  40 G of the connector  20 G, and the buffering layer is also attached on the surface of each of the curved wall  410 G, the side inclined face  601 G, the top curved face  602 G, the inside wall  42 G, the engaging face  431 G, the contact face  432 G, the top wall  41 G, the side face  240 G and the top face  220 G of the upright portion  22 G. Besides, the buffering layer is attached to the surface of the groove  221 G of the top face  220 G The buffering layer is made by the material that is softer than that of the connector  20 G so that the connector  20 G is able to be deformed as desired when the panel  10 G is connected with the connector  20 G. After the panels  10 G are connected with the connector  20 G, the buffering layer provides a buffering feature between the panels  10 G and the connector  20 G to reduce the friction between the panels  10 G and the connector  20 G to solve the problems of shrinking and expanding due to change of temperature or the problems of shifting due to pushing to generate noise. 
     The buffering layer is made by soft material so that the buffering layer can be made with the connector  20 G by way of double-layer extruding. 
     For the ninth embodiment,  FIG. 67  shows the embodiment based on the embodiment disclosed in  FIG. 49 ,  FIG. 68  shows the embodiment based on the embodiment disclosed in  FIG. 64 , and  FIG. 69  shows the embodiment based on the embodiment disclosed in  FIG. 65 . 
     As shown in  FIG. 67 , the top face  220 H of the locking piece  24 H of the connector  20 H has a buffering plate  226 H extending from the center thereof. 
     As shown in  FIG. 68 , the top face  220 H′ of the locking piece  24 H′ of the connector  20 H′ has a buffering plate  226 H′ extending from the center thereof. 
     As shown in  FIG. 69 , the top face  220 H″ of the locking piece  24 H″ of the connector  20 H″ has a buffering plate  226 H″ extending from the center thereof. 
     Taken the embodiment in  FIG. 69  as an example, the connector  20 H″ basically the same as that in the  FIG. 65 , the difference is that the top face  220 H″ of the locking piece  24 H″ of the connector  20 H″ has a buffering plate  226 H″ extending from the center thereof. The buffering plate  226 H″ is made by the material that is softer than the material of the connector  20 H′ so that the buffering plate  226 H″ can be made with the connector  20 G by way of double-layer extruding. 
     When the connection  20 H″ is connected with the panels on two sides of the connector  20 H″, the buffering plate  226 H″ is clamped between the top protrusions of the two panels to provide a separation between the top protrusions of the two panels. The buffering plate  226 H″ fills the space between the top protrusions of the two panels, and also ensures that there will be no noise generated due to friction between the top protrusions of the two panels. 
     For the tenth embodiment,  FIG. 70  discloses the panel  10 I which is a triangular panel which has a first surface, a second surface which is located opposite to the first surface, and three sides, wherein at least two of the three sides has a tongue  301 . As shown in  FIG. 71 , the panels  10 I are cooperated with the connectors  201  to be arranged to form a specific pattern. When connecting the panels  10 I, the panels  10 I do not need to lift one side thereof so that the pattern as disclosed in  FIG. 72  can be made. 
     In the tenth embodiment, the panels  10   i  and the connector  20   i  ca be cooperated with the tongues and engaging slots of the multiple embodiments described above to achieve the purpose of the present invention. 
       FIGS. 73 and 74  show the panels are connected to each other, wherein the third embodiment is taken as an example to describe. Because the panels  10 B and the connectors  20 B are connected to each other by way of pressing, so that the connector  30 B are respectively located on the four sides of the panels, and the panels  20 B are easily connected to each other by the connectors  30 B. 
       FIG. 75  shows the elongate panels are connected to each other along the longitudinal direction thereof.  FIG. 76  shows that four elongate panels are connected to each other to form a unit, and four units are composed to form a square combination.  FIG. 77  shows that multiple panels are connected to each other to form a transverse S shape combination. Because the panels are connected to the connectors of the present invention by way of pressing, the tongues of the panels are engaged with the engaging slots of the connectors without lifting one side of the panels, so that the panels can be connected to each other in different ratios of the length-and-width to form desired patterns and shapes. 
     While we have shown and described the embodiment in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.