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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     The present invention relates to a building panel and, more particularly, to a building panel which may be assembled in an interengaging manner with at least one other adjacent like building panel. 
     WO 2004/074593 discloses quadrilateral building panels which have at least two degree rotational symmetry when rotated about a central axis extending perpendicularly to a plane containing a major surface of the panel. A structure can be built using a plurality of these panels assembled in an interengaging manner and adjacent panels may be secured to each other by locking cams. However, the document does not disclose how locking cams could secure adjacent building panels to each other so that their major planes are either substantially parallel and coincident or substantially perpendicular. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a building panel which is arranged to interengage with at least one other adjacent like panel that solves this problem. 
     To this end, the invention consists in a building panel having a major plane and being configured to interengage with at least one other adjacent like panel, the panel having: 
     two major side surfaces which are at least substantially parallel to the major plane, and at least three major edge surfaces substantially forming a perimeter of the panel; 
     an engaging means first portion at one said major edge surface; 
     an engaging means second portion comprising three parts situated respectively at the two major side surfaces and at one said major edge surface, each said part being adjacent to at least one other said part; and 
     at least one of said engaging means first portion and said engaging means second portion part is situated at each said major edge surface 
     whereby the engaging means first portion is latchingly engagable with any one of the engaging means second portion parts of said adjacent like panel so that the major planes of the two panels, when interengaged, are selectively substantially parallel and coincident or substantially perpendicular. 
     Each said part of the engaging means second portion may comprise at least one recess in said major edge surface or said major side surface. The engaging means second portion may have a pin in each said recess. 
     The engaging means first portion may be arranged to extend from said major edge surface. The engaging means first portion may be retractably extendable from said major edge surface. 
     At least one said major edge surface may have said engaging means first portion and one said part of said engaging means second portion. At least one said major edge surface may include at least one inwardly stepped portion and at least one outwardly stepped portion and each inwardly stepped portion is dimensioned to receive an outwardly stepped portion on an edge surface of an adjacent panel. 
     The engaging means first portion preferably comprises an over-centre camlock mechanism for latchingly engaging the pin. 
     The building panel may have at least two degree rotational symmetry when rotated about a central axis extending perpendicularly to said major plane. 
     A structure may be formed which comprises a plurality of said building panels as described above and assembled in an interengaging manner. 
     A structure may be formed which includes at least one said building panel as described above, and at least one panel comprising at least part of a column or beam, said column or beam panel having engaging means first and/or second portions for latchingly engaging any one of the engaging means second portion parts and/or the engaging means first portion of said building panel. The columns and beams having said engaging means first and/or second portions can be utilized to provide additional strength for taller (e.g. multi-storey) buildings and larger spans than would be possible using the building panels alone. 
     The structure may include three said building panels, 
     the first panel of said three panels having said engaging means second portion, 
     the second panel of said three panels having said engaging means first portion engaging one said part of the engaging means second portion of said first panel, and 
     the third panel of said three panels having said engaging means first portion engaging another one of said parts of the engaging means second portion of said first panel, wherein the major planes of said three panels form a “T”. 
     The structure may include a fourth said building panel, said fourth panel engaging another one of said parts of the engaging means second portion of said first panel, wherein the major planes of said four panels form a cross. 
     In a preferred embodiment, one major side surface of the building panel has access means for providing access for a tool to operate the engaging means first portion. The access means may only be accessible from inside the structure ensuring that the structure is secure. Nevertheless, the structure can be dismantled or modified at any time. Alternatively, both major side surfaces of the building panel may have access means for providing access for a tool to operate the engaging means first portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:— 
         FIG. 1  is a plan view of a building panel constructed in accordance with one embodiment of the invention; 
         FIG. 2  is a perspective view of a hook and cam mechanism for the building panel; 
         FIG. 3  is a perspective sectional view through an outwardly stepped portion of the building panel; 
         FIGS. 4 to 6  are perspective views of two building panels being interengaged so as to be parallel, coplanar and adjoining; 
         FIGS. 7 and 8  are perspective views of the interengaged panels of  FIGS. 5 and 6  having additional panels connected to them; 
         FIG. 9  is a perspective view of a structure constructed with the building panels; 
         FIG. 10  is a perspective view of a portion of two building panels interengaged so as to be perpendicular with one another and having a column attached thereto; 
         FIG. 11  is a sectional view taken along lines  11 - 11  shown on  FIG. 10 ; 
         FIG. 12  is a perspective view of part of a beam for connection to a building panel; 
         FIG. 13  is a perspective view of a structure incorporating the building panels of  FIG. 1  and the beams of  FIG. 12 ; 
         FIG. 14  is a perspective view of a modified outwardly stepped portion of the building panel; 
         FIG. 15  is a sectional view taken along lines  15 - 15  shown on  FIG. 14 ; 
         FIG. 16  is a plan view of a building panel constructed in accordance with another embodiment of the invention; 
         FIG. 17  is a perspective view of two building panels illustrated in  FIG. 16  being interengaged so as to be parallel, coplanar and adjoining; 
         FIG. 18  is a longitudinal section through the panels of  FIG. 17 ; 
         FIG. 19  is a perspective view of a portion of the two building panels shown in  FIG. 17  interengaged so as to be perpendicular with one another; and 
         FIG. 20  is a sectional view taken along lines  20 - 20  shown on  FIG. 19 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1  of the accompanying drawings, the building panel  1  is generally rectangular in plan and has opposed major end edge surfaces  2  interconnected by opposed major side edge surfaces  3  defining a surrounding perimeter edge  4  made up from alternating relatively inwardly stepped portions  5  and relatively outwardly stepped portions  6 . The panel  1  includes one inwardly stepped portion  5  and one outwardly stepped portion  6  or lug along each major end edge surface  2  and two inwardly stepped portions  5  and two outwardly stepped portions  6  or lugs along each major side edge surface  3 . The length of each inwardly stepped portion  5  is dimensioned to receive a complementary outwardly stepped portion  6  of an adjacent like panel  1  which is coplaner or orthogonal and the stepped portions  5 , 6  are arranged so that the panel  1  has two degree rotational symmetry when rotated about a central axis  60  extending perpendicularly to a major side surface  16  of the panel  1 . 
     Each inwardly stepped portion  5  has a hook and cam mechanism or an over-centre camlock mechanism  7  which is shown in  FIG. 2 . Referring to  FIG. 4 , the mechanism  7  has a mounting  8  mounted beneath the edge surface  9  of the inwardly stepped portion  5 . The hook  10  or latch of the mechanism  7  is rotatably mounted in the mounting  8  and the axis of rotation is midway along the length of the inwardly stepped portion  5 . One side of the panel  1  has a hole  11  to provide access for a suitable tool, such as an Allen key, to rotate the hook  10  about the mounting  8  so that it protrudes from a slot  12  or recess in the edge surface  9 . Final travel of the tool operates an over-centre cam (not shown) within the camlock mechanism  7  to lock the hook  10 . The slot  12  is of a sufficient length in order to fully contain the hook  10  when the hook  10  is rotated by the tool so as to be unlocked and fully retracted before being locked in an open position ensuring that personnel and other panels cannot be damaged by protruding hooks. A suitable hook and cam mechanism or over-centre camlock mechanism  7  is described in U.S. Pat. No. 6,409,235. 
     Referring to  FIG. 3 , each outwardly stepped portion  6  has a slot  13  or recess extending longitudinally along its edge surface  14 . Each portion  15  of the two major side surfaces  16  of the building panel  1  which form the sides of each outwardly stepped portion  6  also has a longitudinally extending slot  17  or recess. The slots  13 , 17  are all located midway along the length of the outwardly stepped portion  6 . A hole  18  extends from one side portion surface  15  into the outwardly stepped portion  6  and a pin  19  is inserted into the hole  18  and crosses the slot  13  beneath the edge surface  14 . The bottom of the outwardly stepped portion  6  has a pair of holes  20  extending therein and a pin  21  is inserted into each hole  20  which crosses the slot  17  beneath the side portion surfaces  15 . The axes of the pins  19 , 21  are all located along the middle of the outwardly stepped portion  6 . The outwardly stepped portion  6  is attached to the main body of the building panel  1  so that the holes  20  in the bottom are sealed. In a preferred embodiment, each pin  19 , 21  comprises a metal dowel. 
     Referring to  FIGS. 4 to 8 , a first building panel  1   a  is shown having a second building panel  1   b  attached so as to be coplanar and adjoining and third and fourth building panels  22   a , 22   b  attached which are perpendicular to the first and second building panels  1   a , 1   b . The first and second panels  1   a , 1   b  are the same and the third and fourth panels  22   a , 22   b  are similar to the first and second panels  1   a , 1   b  except that they do not have inwardly and outwardly stepped portions on the edge surface so that they can abut the first and second panels  1   a , 1   b.    
     The inwardly stepped portion  5   a  of the first building panel  1   a  is arranged to receive the outwardly stepped portion  6   b  of the second building panel  1   b  and the outwardly stepped portion  6   a  of the first building panel  1   a  is arranged to be received by the inwardly stepped portion  5   b  of the second building panel  1   b  ( FIG. 4 ). 
     When the two panels  1   a , 1   b  are engaged the hook  10  of the over-centre camlock mechanism  7  of the inwardly stepped portion  5   b  of the second building panel  1   b  is rotated by a tool so that it is received by the slot  13  in the edge surface  14  of the outwardly stepped portion  6   a  of the first building panel  1   a  so that it hooks around the pin  19  therein ( FIGS. 5 and 6 ). Final travel of the tool operates the over-centre cam within the mechanism  7 , pulling the two panels  1   a , 1   b  together with significant force ensuring that they cannot come together without application of the tool. In the same way, the hook of the over-centre camlock mechanism (not shown) in the inwardly stepped portion  5   a  of the first building panel  1   a  is rotated so that it hooks around the pin in the outwardly stepped portion  6   b  of the second building panel  1   b.    
     The third panel  22   a  is then placed perpendicularly against the interengaged first and second panels  1   a , 1   b  and the hooks  10  of the over-centre cam mechanisms  7  of the third panel edge surface  23   a  adjacent the panels  1   a , 1   b  are rotated so that they are received by the corresponding slots  17  in the side portion surface  15 ′ of the outwardly stepped portions  6   a , 6   b  of the first and second panels  1   a , 1   b  and engage the pins  21  therein ( FIG. 7 ). The interengaged panels  1   a , 1   b , 22   a  form a “T”. 
     In the same way, the fourth panel  22   b  is placed opposite the third panel  22   a  so that the over-centre camlock mechanisms  7  of the fourth panel  22   b  for the edge surface  23   b  adjacent the panels  1   a , 1   b  are rotated so that they engage the pins  21  in the opposite side portion surface  15 ″ of the outwardly stepped portions  6   a , 6   b  ( FIG. 8 ). The interengaged panels  1   a , 1   b , 22   a , 22   b  form a cross. 
     The third and fourth panels  22  can form internal partitions of an interlocked structure  24 , such as that illustrated in  FIG. 9 , made from the first and second panels  1  enabling them to butt up against, and lock into, the structure  24 . Some of the building panels of the structure  24  are shown as having an opening which contains a door  25  or window  26 . 
     Referring to  FIGS. 10 and 11 , two building panels  1   a ,  1   b  are shown interengaged so that their major planes are perpendicular and a column  27  is also attached. The column  27  is similar to the third and fourth building panels  22   a , 22   b  of  FIGS. 7 and 8  except that it has pairs of over-centre camlock mechanisms  7  for opposite edge surfaces  28  and both of these surfaces  28  do not have any inwardly and outwardly stepped portions. 
     The inwardly stepped portion  5   a  of the first building panel  1   a  receives the outwardly stepped portion  6   b  of the perpendicular second building panel  1   b  and the outwardly stepped portion  6   a  of the first building panel  1   a  is received by the inwardly stepped portion of the second building panel  1   b . The hook  10  of the over-centre camlock mechanism  7  of the inwardly stepped portion  5   a  of the first panel  1   a  engages the pin  21  in the slot  17  of the second building panel side portion surface  15  adjacent the first building panel  1   a . In the same way, the hook of the over-centre camlock mechanism (not shown) in the inwardly stepped portion of the second building panel  1   b  engages the pin in the slot of the first building panel side portion surface adjacent the second building panel  1   b . The column  27  is aligned with the first building panel  1   a  so that their major side surfaces are coplaner and adjacent and the hook  10  of the over-centre camlock mechanisms  7  of the column edge surface  28  adjacent the interengaged panels  1   a , 1   b  engages the pins  21  in the slot  17  of the second building panel side portion surface  15  adjacent the column  17  and the pins (not shown) in the slots of the first building panel outwardly stepped portion edge surfaces. Such latching columns  27  can be incorporated into the sides of buildings. 
     A beam is illustrated in  FIG. 12  which is the same as the column  27  illustrated in  FIGS. 10 and 11  except that it is orientated in a different direction. A two storey building  30  using building panels  1  and beams  29  is illustrated in  FIG. 13 . The beams  29  are parallel to one another, spaced apart at regular panel width distances and lock the ceiling building panels  1   c  of the ground floor to the floor building panels  1   d  of the first floor creating a very strong structure as pseudo-box girders are formed from the ceilings, floors and beams  29  latched to both at regular intervals. The beams  29  also provide between-floor voids which can house services. 
     A building panel  30  having a modified outwardly stepped portion  31  or lug is illustrated in  FIGS. 14 and 15 . The outwardly stepped portion  31  uses an extruded section and is hollow. It has an inverse U shape  32  in cross-section with a pair of bottom flanges  33  extending towards each other from the base of the inverse U. Each slot  13 , 17  is formed from a pair of walls  34  extending inwardly from the surface  14 , 15  of the outwardly stepped portion  31  containing the slot  13 , 17 . The slot  13  for the edge surface  14  has a pin  35  which extends from a hole  36  in one side portion surface  15  of the outwardly stepped portion  31  and through aligned holes  37  in the walls  34 . The walls  34  of the other two slots  17  also have a pair of aligned holes  38  through each of which there extends a pin  39 . 
     The building panel  30  has a pair of channels  40 , each on opposite sides to each other for receiving the bottom flanges  33  of the outwardly stepped portion  31 . Each channel  40  also receives the top flange  41  of a sheet  42  which covers a major side surface of the building panel  30 . The building panel  30  protrudes above the channel  40  for a length coincident with the length of the outwardly stepped portion  31 . The edge surface  43  of the protrusion has a centrally aligned recessed channel  44  along the length of the protrusion. 
     A building panel  50  without stepped portions is illustrated in  FIG. 16 . 
     Referring to  FIGS. 17 and 18 , a first building panel  50   a  is shown having a second building panel  50   b  attached so as to be coplanar and adjoining. Along the adjoining major edge surfaces  51  of the two interengaged panels  50   a , 50   b , the hooks  10  of the over-centre camlock mechanisms  7  of the first panel  50   a  are arranged to engage the pins  19  in the slots  13  in the second building panel  50   b  and the hooks  10  of the over-centre camlock mechanisms  7  of the second panel  50   b  are arranged to engage the pins  19  in the slots  13  in the first building panel  50   a.    
     Referring to  FIGS. 19 and 20 , the first and second building panels  50   a , 50   b  are attached so as to be perpendicular to one another. A major edge surface  51  of the first panel  50   a  adjoins a major side surface  52  of the second panel  50   b  so that the hooks  10  of the over-centre camlock mechanisms  7  of the first panel major edge surface  51  are arranged to engage the pins  21  in the slots  17  in the adjoining second building panel major side surface  52 . 
     In  FIGS. 17 to 20 , the unused over-centre camlock mechanisms  7  are shown as being extended for clarity but they would normally be retracted. 
     Whilst particular embodiments have been described, it will be understood that various modifications may be made without departing from the scope of the invention. A panel may have just over-centre camlock mechanisms along one major edge surface and the slots along an opposite edge surface and the portion of the major side surface adjacent the major edge surface. The panels are shown as being rectangular but they also may be substantially square or triangular in plan or may be any other appropriate geometric shape.

Summary:
A building panel ( 1 ) has a major plane and is configured to interengage with at least one other adjacent like panel. The panel ( 1 ) has two major side surfaces ( 16 ) which are parallel to the major plane, and four major edge surfaces ( 2, 3 ) forming a perimeter ( 4 ) of the panel ( 1 ). An over-center camlock mechanism ( 7 ) is retractably extendable from each major edge surface ( 2, 3 ). Each major edge surface ( 2, 3 ) has a recess with an associated recess ( 17 ) at each major side surface ( 16 ), so that each recess is adjacent to at least one other recess. There is a pin in each recess and any over-center camlock mechanism ( 7 ) is latchingly engageable with the pin in any one of the recesses of the adjacent like panel so that the major planes of the two panels, when interengaged, are selectively parallel and coincident or perpendicular.