Patent Publication Number: US-11660767-B2

Title: Easily disassembled folding knife

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/181,254, filed Feb. 22, 2021, which is a continuation of U.S. patent application Ser. No. 16/380,640, filed Apr. 10, 2019, now U.S. Pat. No. 10,974,398, which is a continuation of U.S. patent application Ser. No. 15/855,872, filed Dec. 27, 2017, now U.S. Pat. No. 10,272,576, which is a continuation of U.S. patent application Ser. No. 15/444,047, filed Feb. 27, 2017, now U.S. Pat. No. 9,862,106, which is a continuation of U.S. patent application Ser. No. 14/197,120, filed Mar. 4, 2014, now U.S. Pat. No. 9,597,809, which claims the benefit of U.S. Provisional Patent Application No. 61/772,449, filed Mar. 4, 2013. All of the related applications are incorporated by reference herein. 
    
    
     FIELD 
     The present disclosure relates to folding knives and, more particularly, to folding knives configured to be easily disassembled. 
     BACKGROUND 
     Folding knives are available in various configurations. In some of these configurations, the blade of a folding knife can be removable to facilitate cleaning, sharpening, replacement, or storing of a blade. As examples, U.S. Pat. Nos. 7,370,421 and 7,716,839 describe a knife having a removable blade. Because folding knives having removable blades are particularly advantageous in harsh conditions (i.e., in situations where a knife is likely to become dirty or dull, and thus where the ability to clean, sharpen, or replace a blade in the field is important), it would be beneficial to provide a folding knife with a removable blade having as simple a structure as possible. Simpler configurations can help to ensure that the blade remains easily removable after use in harsh conditions and that removal of the blade can be accomplished as quickly and reliably as possible. Accordingly, simple mechanisms allowing a folding knife to be easily disassembled are desirable. 
     SUMMARY 
     The present disclosure is directed toward new and non-obvious methods and apparatuses relating to folding knives. In one embodiment, a folding knife comprises a handle portion including first and second, laterally spaced side portions defining a blade-receiving cavity therebetween, a pivot element coupled to the first side portion, a blade pivotably connected to the pivot element of the handle portion and pivotable relative to the handle portion about the pivot element between a closed position and an open position, and a locking element having a non-circular shape coupled to the pivot element. 
     The second side portion can include a non-circular opening and can be adapted to be rotatable relative to the first side portion about an axis extending through the locking element between a first position and a second position, wherein when the second side portion is in the first position, the opening is rotationally offset from the locking element, and the locking element blocks lateral movement of the second side portion relative to the first side portion, and wherein when the second side portion is in the second position, the opening is rotationally aligned with the locking element to allow the locking element to be moved through the opening to permit lateral movement of the second side portion away from the first side portion along the axis. 
     In other embodiments, the folding knife can also include a securing mechanism configured to selectively retain the second side portion against rotational movement relative to the first side portion when the second side portion is in the first position. The second side portion can be rotationally aligned with the first side portion when the second side portion is in the first position. The pivot element can extend through an opening in the blade and the blade can be removable from the pivot element in a direction along the axis when the second side portion is first moved away from the first side portion along the axis. Finally, the locking element can have a hexagonal cross section and the opening can be hexagonal. 
     In some embodiments, a folding knife comprises a handle portion comprising first and second, laterally spaced side portions defining a blade-receiving cavity therebetween, a pivot element coupled to the first side portion and defining a pivot axis, a blade pivotably connected to the pivot element of the handle portion and pivotable relative to the handle portion about the pivot axis between a closed position and an open position, and a locking element having a non-circular shape coupled to the pivot element, wherein the second side portion comprises a non-circular opening, the second side portion configured to move the non-circular opening between a first, locking position and a second, release position, wherein when the non-circular opening is in the first position, the opening is rotationally offset from the locking element, and the locking element blocks lateral movement of the second side portion relative to the first side portion, and wherein when the non-circular opening is in the second position, the opening is rotationally aligned with the locking element to allow the locking element to be moved through the opening to permit lateral movement of the second side portion away from the first side portion along the pivot axis. 
     In some embodiments, a folding knife comprises a handle portion comprising first and second, laterally spaced side portions defining a blade-receiving cavity therebetween, a pivot element coupled to the first side portion, a blade pivotably connected to the pivot element of the handle portion and pivotable relative to the handle portion about the pivot element between a closed position and an open position, and a locking element having a non-circular shape coupled to the pivot element, wherein the second side portion comprises a non-circular opening and is adapted to be rotatable relative to the first side portion about an axis extending through the locking element between a first position and a second position, wherein when the second side portion is in the first position, the opening is rotationally offset from the locking element, and the locking element blocks lateral movement of the second side portion relative to the first side portion, and wherein when the second side portion is in the second position, the opening is rotationally aligned with the locking element to allow the locking element to be moved through the opening to permit lateral movement of the second side portion away from the first side portion along the axis. 
     In some embodiments, a method of assembling a folding knife comprises sliding an opening in a blade of the folding knife over a non-circular locking portion, an intermediate portion, and a pivot element of a first side portion of a handle of the knife, positioning a second side portion such that a non-circular opening in the second side portion is rotationally aligned with the locking portion, sliding the opening of the second side portion over the locking portion and the intermediate portion, and rotating the opening such that the opening is rotationally offset from the locking portion. 
     In some embodiments, a folding knife comprises a handle portion comprising first and second, laterally spaced side portions defining a blade-receiving cavity therebetween, a pivot element coupled to the first side portion and defining a pivot axis, a blade pivotably connected to the pivot element of the handle portion and pivotable relative to the handle portion about the pivot axis between a closed position and an open position, and a blade sharpening element coupled to the inner surface of one of the first and second side portions, wherein the first and second side portions can be disassembled from each other to permit use of the sharpening element. 
     In some embodiments, a folding knife comprises a handle portion comprising first and second, laterally spaced side portions defining a blade-receiving cavity therebetween, a pivot element coupled to the first side portion and defining a pivot axis, a blade pivotably connected to the pivot element of the handle portion and pivotable relative to the handle portion about the pivot axis between a closed position and an open position, at least one recessed compartment formed in the inner surface of one or both of the first and second side portions, and one or more tools stored in the compartment, wherein the first and second side portions can be disassembled from each other to gain access to the one or more tools in the compartment. 
     In some embodiments, a folding knife comprises a handle portion comprising first and second, laterally spaced side portions defining a blade-receiving cavity therebetween, a pivot element coupled to the first side portion and defining a pivot axis, a blade pivotably connected to the pivot element of the handle portion and pivotable relative to the handle portion about the pivot axis between a closed position and an open position, and a locking element having a non-circular shape coupled to the pivot element, wherein the second side portion comprises a lock that is rotatable with respect to the locking element, wherein the lock comprises a non-circular opening such that rotation of the lock with respect to the locking element causes the non-circular opening to rotate between a first, locking position and a second, release position, wherein when the non-circular opening is in the first position, the opening is rotationally offset from the locking element, and the locking element blocks lateral movement of the second side portion relative to the first side portion, and wherein when the non-circular opening is in the second position, the opening is rotationally aligned with the locking element to allow the locking element to be moved through the opening to permit lateral movement of the second side portion away from the first side portion along the pivot axis. 
     The foregoing and other objects, features, and advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of an exemplary folding knife. 
         FIGS.  2  and  3    are side views of the folding knife of  FIG.  1    in an open configuration and a closed configuration, respectively. 
         FIGS.  4 A and  4 B  show a perspective view and a perspective, exploded view of another exemplary folding knife, respectively. 
         FIGS.  5  and  6    show side and bottom views, respectively, of a side portion of the folding knife of  FIGS.  4 A and  4 B . 
         FIG.  7    shows a bottom cross-sectional view of a portion of the folding knife of  FIGS.  4 A and  4 B . 
         FIG.  8    shows the folding knife of  FIGS.  4 A and  4 B  in a partially assembled state. 
         FIG.  9    shows a perspective, exploded view of another exemplary folding knife. 
         FIG.  10    shows a bottom cross-sectional view of a portion of the folding knife of  FIG.  9   . 
         FIGS.  11 - 12    show a folding knife having an exemplary secondary locking mechanism. 
         FIGS.  13 - 14    show a folding knife having another exemplary secondary locking mechanism. 
         FIG.  15 A  shows a perspective, exploded view of another exemplary folding knife. 
         FIGS.  15 B- 19    show various components of the folding knife of  FIG.  15 A . 
         FIG.  20    shows another exemplary folding knife. 
         FIG.  21    shows a perspective, exploded view of the folding knife of  FIG.  20   . 
         FIG.  22    shows a partially assembled view of the folding knife of  FIG.  20   . 
         FIG.  23    shows a bottom cross-sectional view of a portion of the folding knife of  FIG.  20   . 
         FIG.  24    shows another exemplary folding knife. 
         FIG.  25    shows a partially assembled view of the folding knife of  FIG.  24   . 
         FIG.  26    shows a perspective, exploded view of the folding knife of  FIG.  24   . 
         FIGS.  27 - 28    each show a partially assembled view of the folding knife of  FIG.  24   . 
         FIG.  29    shows another exemplary folding knife in a closed configuration. 
         FIG.  30    shows the folding knife of  FIG.  29    in an open configuration. 
         FIGS.  31 - 34    show various components of the folding knife of  FIG.  30   . 
         FIG.  35    shows a perspective, exploded view of the folding knife of  FIG.  30   . 
         FIG.  36    shows one embodiment of a side portion of the knife of  FIG.  30   . 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure concerns folding knives that can be more easily disassembled than known folding knives, such as for cleaning or replacing a blade or other components. For example, folding knives disclosed herein can be manually disassembled, that is, disassembled without the use of additional tools (e.g., without a screwdriver, etc.). In some cases, easily disassembled folding knives include a handle having first and second side portions having complementary locking elements which can prevent the side portions from being separated from one another. 
     Referring to  FIGS.  1 - 3   , a first embodiment of a folding knife  100  can include a handle portion  102  and a blade  104 . The blade  104  can be pivotably connected to the handle  102  such that the blade  104  can be pivoted about an axis  106  between an open position for using the blade (as shown in  FIG.  2   ) and a closed position for storing the blade (as shown in  FIG.  3   ). The handle  102  can include a first side portion  108  and a second side portion  110 . The first and second side portions can be spaced apart from each other by a distance, thereby defining a blade receiving channel  112  between the two side portions for receiving the blade when it is pivoted to its closed position. As shown in  FIG.  2   , the first side portion  108  can include a leaf spring  114  (known as a “liner lock” or a “frame lock”) that is biased into a position engaging the rear edge of the tang of the blade  104  to retain the blade in the open position, as is known in the art. 
       FIGS.  4 - 8    illustrate one embodiment of a folding knife  200  including a handle portion  202  and a blade  204  pivotably connected to the handle  202  for pivoting motion about an axis  206 . The handle  202  can include a first side portion  208  and a second side portion  210 .  FIG.  4 A  illustrates a perspective view of the knife  200 .  FIG.  4 B  illustrates an exploded perspective view of the knife  200 .  FIGS.  5  and  6    illustrate side and bottom views, respectively, of the first side portion  208 . As shown, a primary raised cylindrical protrusion  212 , which functions as a pivot element or pivot pin for the blade, can extend laterally from the inner surface of the first side portion  208 . The central longitudinal axis of the primary cylindrical protrusion  212  can be aligned with the pivot axis  206 . As also shown in  FIGS.  5 - 6   , a secondary raised cylindrical portion  214  can extend laterally from the inner side surface of the primary cylindrical protrusion  212 . As shown, the diameter of the secondary cylindrical portion  214  can be smaller than the diameter of the primary cylindrical portion  212 , and the central longitudinal axis of the secondary protrusion  214  can be aligned with the central longitudinal axis of the primary protrusion  212  and the pivot axis  206 . 
     As also shown in  FIGS.  5 - 6   , a hexagonal locking portion, or locking element,  216  can be attached to the inner side surface of the secondary protrusion  214 . As shown, the width W of the locking portion  216  can be greater than the diameter of the secondary protrusion  214 , so that a locking channel  218  is thereby defined between the primary protrusion  212  and the locking portion  216 . The width of the channel  218  (the distance between the pivot pin  212  and the locking element  216 ) is sized to receive the second side portion  210 , as further described below. As shown in  FIGS.  5 - 6   , the thickness of each of the first side portion  208 , the primary protrusion  212 , the secondary protrusion  214 , and the locking portion  216  along the pivot axis are approximately the same. In alternative embodiments, however, the precise thicknesses of each of these components along the pivot axis can be any suitable length, and are independent of one another. 
     As best shown in  FIG.  4 B , the second side portion  210  can include a hexagonal opening  220  that extends through the entire second side portion  210 . The hexagonal opening  220  can be advantageously sized so that it is only slightly larger than the hexagonal locking portion  216  of the first side portion  208 . The opening  220  can be further configured such that when the first and second side portions are placed adjacent one another in an assembled, as-used configuration, the hexagonal shape of the opening  220  is rotationally offset about the pivot axis  206  from the hexagonal shape of the locking portion  216 . As best shown in  FIG.  4 B , the hexagonal shape of the opening  220  can be rotationally offset from the hexagonal shape of the locking portion  216  by approximately 30 degrees ( 1/12 of a full rotation), such that the corners of the two hexagonal shapes are rotationally offset from each other as far as possible. The blade  204  can have a circular opening  222 . The circular opening  222  can be sized so that its diameter is larger than both the width of the locking portion  216  and the diameter of the primary protrusion  208 . 
     While the illustrated embodiment includes a hexagonal locking element  216  and corresponding hexagonal opening  220 , the locking element  216  and the corresponding opening  220  can be any of various shapes. In general, a knife can comprise a locking element (e.g., locking element  216 ) having a non-circular cross-sectional shape (taken along a plane perpendicular to the pivot axis  206 ) that extends through an opening (e.g., opening  220 ) of the same or similar shape in a side portion of the handle. The locking element  216  and corresponding opening  220  can be any of various shapes, such as, without limitation, square, triangular, cruciform (cross shaped), etc. It should be noted that in any of the embodiments disclosed herein, wherever a first component has a non-circular cross-sectional shape that fits though a correspondingly shaped opening in a second component, the shape of the first component and the opening can be any of various shapes, including but not limited to a square, hexagon, triangle, cruciform, oval, etc. 
     In use, the non-circular locking element cooperates with the non-circular opening to prevent lateral separation of the side portions  208 ,  210  of the handle when the locking element is rotationally offset from the opening. Conversely, rotating the second side portion  210  such that the opening  220  is rotationally aligned with the locking element  216  allows lateral separation of the side portions  208 ,  210  of the handle. In certain embodiments, the shape of the opening  220  need not correspond exactly to the cross-sectional shape of the locking element  216 . In particular, the opening  220  in the side portion  210  can have any non-circular shape that is sized and shaped: (1) to allow the locking element  216  to slide through the opening  220  when the side portion  210  is in a first rotational position in which the opening  220  is rotationally aligned with the locking element  216  and (2) to block the locking element  216  from sliding through the opening  220  when the side portion  210  is in a second rotational position in which the opening  220  is rotationally offset from the locking element  216 . As used herein, the term “rotationally aligned” means that the opening  220  in the side portion  210  is in a rotational position relative to the locking element  216  about a central axis (e.g., pivot axis  206 ) extending through the opening and the locking element such that the locking element can fit or slide through the opening in a direction along the axis  206 . The term “rotationally offset” means that the opening  220  in the side portion  210  is in a rotational position relative to the locking element  216  about the central axis  206  extending through the opening and the locking element such that the locking element cannot fit or slide through the opening in a direction along the axis  206 . 
     The folding knife  200 , comprising the first side portion  208 , the second side portion  210 , and the blade  204 , as described above, can be assembled by sliding the opening  222  of the blade over the locking portion  216 , the secondary protrusion  214 , and the primary protrusion  212 , such that the blade  204  rests against the first side portion  208 . Referring to  FIG.  8   , the folding knife  200  can be further assembled by positioning the second side portion  210  so that it is rotationally offset around the axis  206  from the first side portion  208  by about 30 degrees, so that the hexagonal shape of the opening  220  and the hexagonal shape of the locking portion  216  are generally aligned, and then sliding the hexagonal opening  220  of the second side portion  210  over the locking portion  216  and the secondary protrusion  214  until the second side portion  210  rests within the locking channel  218  adjacent the blade. In this configuration, the central longitudinal axis of the protrusions  212 ,  214 , and the locking portion  216 , as well as of the opening  222  in the blade  204  and the opening  220  in the second side portion  210  are aligned with the pivot axis  206 . 
     The second side portion  210  can then be rotated from the position shown in  FIG.  8    until it is rotationally aligned with the first side portion  208 , and such that the hexagonal shape of the opening  220  is rotationally offset from the hexagonal shape of the locking portion  216 . In this configuration, the corners  224  of the locking portion  216  extend beyond the edges of the opening  220 , thereby preventing the second side portion  210  from being removed in a lateral direction away from the first side portion  208 , and thereby also preventing the blade  204  from being removed from the rest of the knife  200 . In order to remove the second side portion  210  from the first side portion  208 , the second side portion  210  can be rotated about 30 degrees from the first side portion  208  such that the corners of the locking portion  216  no longer capture the second side portion  210 , as in the configuration shown in  FIG.  8   , which can then slide laterally away from the first side portion  208  along the axis  206 . Mechanisms for retaining the second side portion  210  against rotation relative to the first side portion  208  in the as-use position are described in detail below. 
     The first side portion  208  can be formed integrally, with the primary cylindrical protrusion  212 , the secondary protrusion  214 , and the locking portion  216  all being formed from a single piece of material, or each of these components can be formed separately and joined later in the fabrication process, such as by welding. Alternatively, the primary protrusion  212 , the secondary protrusion  214 , and the locking portion  216  can be an integral component that is removably secured to the first side portion, such as with a screw or other removable fastener. Each of the components of the knife  200  can be formed of various materials, including metals, plastics, and/or composites. 
       FIGS.  9 - 10    illustrate another embodiment of a folding knife  300  which can include a blade  304  pivotably connected to a handle portion  302  for pivoting motion about an axis  306 . The handle  302  can include a first side portion  308 , a second side portion  310 , a washer  312 , a pivot and locking element  314 , and a locking screw  316 .  FIG.  9    illustrates an exploded perspective view of the knife  300 . 
     The first side portion  308  can include a cylindrical recess  318  formed in the inner surface of the first side portion  308  and having a central longitudinal axis aligned with the pivot axis  306 . A circular opening  320  also having a central longitudinal axis aligned with the pivot axis  306  can extend from the end of the recess  318  to the outer surface of the first side portion  308 . The washer  312  can be configured to be positioned within the recess  318 . The washer  312  can be secured within the recess  318 , such as with an adhesive or a press-fit configuration, to prevent the washer from being removed when the knife is disassembled. 
     The pivot and locking element  314  can comprise a first cylindrical portion  322  coupled to a second cylindrical portion  324 , itself coupled to a hexagonal locking portion  326 . The cylindrical portion  322  functions as the pivot pin or pivot element for the blade. The first cylindrical portion  322  can have a threaded recess  334  at one end configured to receive the locking screw  316  and can have a diameter which is larger than the diameter of the second cylindrical portion  324 . The hexagonal portion  326  can have a width which is also larger than the diameter of the second cylindrical portion  324 . Thus, a locking channel  328  can be defined between the first cylindrical portion  322  and the hexagonal portion  326  for receiving the second side portion  310 . The screw  316  can be configured to engage the threaded recess of the first cylindrical portion  322 , and can have a head having a diameter larger than the diameter of the opening  320 . 
     An assembly  336  can comprise the first side portion  308 , washer  312 , pivot and locking element  314 , and locking screw  316 . The assembly  336  has a structure similar to that of the first side portion  208  of the knife  200 . The blade  304  can have a cylindrical opening  338  which has a diameter greater than the diameters of the first cylindrical portion  322  and the second cylindrical portion  324 , and greater than the width of the hexagonal portion  326 . 
     The second side portion  310  can include a hexagonal recess  330  in communication with a cylindrical cavity  332  contained entirely within the second side portion  310 . The hexagonal recess  330  can advantageously be sized so that it is slightly larger than the hexagonal portion  326  of the assembly  336 . When the assembly  336  and the second side portion  310  are placed adjacent one another in an assembled, as-used position, the hexagonal portion  326  seats within the cavity  332  and the hexagonal shape of the recess  330  is rotationally offset about the pivot axis  306  from the hexagonal shape of the portion  326 . The hexagonal shape of the recess  330  can be rotationally offset from the hexagonal shape of the portion  326  by approximately 30 degrees ( 1/12 of a full rotation) such that the corners of the two hexagonal shapes are rotationally offset from each other as far as possible. The cylindrical cavity  332  can be large enough that the hexagonal portion  326  can be situated and freely rotate within it. 
     The folding knife  300 , comprising the assembly  336 , the second side portion  310 , and the blade  304 , as described above, can be assembled by sliding the opening  338  of the blade  304  over the hexagonal portion  326 , second cylindrical portion  324 , and first cylindrical portion  322 , such that the blade  304  rests against the first side portion  308 . The folding knife  300  can be further assembled by positioning the second side portion  310  so that it is rotationally offset around axis  306  from the first side portion  308  by about 30 degrees, so that the hexagonal shape of the recess  330  and the hexagonal shape of the portion  326  are generally aligned, and then sliding the recess  330  of the second side portion  310  over the hexagonal portion  326  and the second cylindrical portion  324  such that the hexagonal portion  326  rests within the cylindrical cavity  332 . In this configuration, the central longitudinal axis of the washer  312 , locking element  314 , locking screw  316 , recess  330 , cavity  332 , and opening  338  can all be generally aligned with the pivot axis  306 . 
     The second side portion  310  can then be rotated until it is rotationally aligned with the first side portion  308 , and such that the hexagonal shape of the recess  330  is rotationally offset from the hexagonal shape of the portion  326 . In this configuration, the corners of the hexagonal portion  326  extend beyond the edges of the recess  330 , thereby preventing the second side portion  310  from being removed laterally away from the assembly  336  (including the first side portion  308 ), and thereby also preventing the blade  304  from being removed from the knife  300 . In order to remove the second side portion  310  from the assembly  336 , the second side portion  310  can be rotated about 30 degrees relative to the assembly  336  such that the corners of the hexagonal portion  326  no longer capture the second side portion  310 , which can then slide away from the assembly  336 . Each of the components of the knife  300  can be formed of various materials, including metals, plastics, and/or composites. 
     In order to further secure the two halves of the handle of a knife to one another, a secondary securing mechanism can be provided which can help to ensure that the two halves do not inadvertently rotate with respect to each other and thereby become unfastened. A variety of such mechanisms can be used, and one example is shown in  FIGS.  11 - 12   . As shown in  FIGS.  11 - 12   , a knife  400  can include a removable first side portion  402  having a distal portion  404  and a proximal portion  406 , and a second side portion  408 . The distal portion  404  can include a notch  410 , and the proximal portion  406  can include one or more slots  412  containing springs  418  and a projection  414  configured to fit within the notch  410 . The second side portion  408  can include one or more projections, or knobs,  416  configured to extend into respective slots  412 . The springs  418  can be retained within the slots  412  by any of various suitable means, for example, by an external cover (not illustrated) situated over the slots  412 . 
     The springs  418  are configured to exert a biasing force that urges the proximal portion  406  toward the distal portion  404  in the direction of arrow  420 , causing the projection  414  to engage the recess  410 , thereby preventing rotation of the distal portion  404  relative to the rest of the handle. The distal portion  404  can be removed by sliding the proximal portion  406  rearwardly in the direction of arrow  422  against the biasing force of the springs until the projection  414  is removed from the slot  410 . The distal portion  404  can then be rotated relative to the hexagonal locking element and slid laterally away from the second side portion  408 , as described in detail above. 
     Another exemplary embodiment of a secondary securing mechanism that can be used with a knife is shown in  FIGS.  13 - 14   .  FIG.  13    shows a knife  500  including a distal portion  502  and a proximal portion  504  of a first side portion of the knife  500  and  FIG.  14    shows a cross sectional view of knife  500  along line  14 - 14  of  FIG.  13   . The secondary locking portion illustrated in  FIGS.  13 - 14    is similar to that illustrated in  FIGS.  11 - 12   , except that it uses a dovetail locking system, rather than a notch and projection to rotationally lock the distal portion  502 , thereby preventing the knife from becoming unfastened. For example, the distal portion  502  can include one or more dovetail-shaped projections  506  that are shaped to mate with respective one or more dovetail-shaped slots  508  of the proximal portion  504 . 
     In another embodiment, a removable spring clip can be used to prevent rotation of the side portions of the handle relative to each other. In one implementation, a clip comprises two opposing resilient legs that can slide onto the first and second side portions  208 ,  210 , thereby providing a clamping force against the side portions to hold them together. 
       FIGS.  15 - 19    illustrate an alternative embodiment of an easily disassembled folding knife  600 . Knife  600  can include a handle  602  and a blade  604 . The handle  602  can include a first side portion  606 , a second side portion  608 , a liner lock portion  610 , and a locking portion  612 . Referring to  FIG.  15 A , the first side portion  606  can include three engagement elements  614 A-C, each having respective recesses  616  which can have flat-oval shapes (e.g., a shape comprising an oval with flat sides). Each engagement element  614  can also include respective generally circular openings  618  extending through the first side portion  606  and respective flat-oval openings  620  extending away from the respective circular openings  618  and through the first side portion  606 . 
     The recesses  616  can be formed in a front surface  622  of the first side portion  606 , which can be the exposed surface of the first side portion  606  when the knife  600  is fully assembled. Further, the flat-oval openings  620  can have a width W1 which is smaller than a width W2 (see  FIG.  19   ) of the recesses  616 , which can be about the same as the diameter of the circular openings  618 , such that a lip or ledge  626  is formed in the first side portion  606 . In some cases, the recesses  616  can be formed by removing material from the first side portion  606 , for example, by removing between about ¼ and about ¾, or by removing about ½ of the thickness of the first side portion  606 . In the illustrated embodiment, the knife  600  includes three engagement elements  614 A-C, but in alternative embodiments, fewer or additional engagement elements can be used. 
     As shown, two of the engagement elements  614 A and  614 B can be located near a distal portion of the handle  602  (and thus can be called distal engagement elements) and a third engagement element  614 C can be located near a proximal portion of the handle  602  (and thus can be called a proximal engagement element). Further, the flat-oval shapes of the respective components of the distal engagement elements  614 A and  614 B can be generally aligned with the length of the first side portion  606 . That is, flat sides of the flat-oval openings  620  and the recesses  616  of the distal engagement elements  614 A,  614 B can be parallel or substantially parallel to the length of the first side portion  606 , a top surface  628  of the first side portion  606 , and/or a bottom surface  630  of the first side portion  606 . 
     The flat-oval shapes of the respective components of the proximal engagement element  614 C can be angularly offset from the length of the first side portion  606 . That is, flat sides of the flat-oval opening  620  and the recess  616  of the proximal engagement element  614 C can be angularly offset from the top surface  628 , bottom surface  630 , and/or the length of the first side portion  606 , and thus from the respective flat sides of the components of the distal engagement elements  614 A,  614 B. The flat sides of the openings  620  of the proximal engagement elements can be offset from the flat sides of the openings  620  of the distal engagement elements by an angle α, which can be, for example, between about 5° and about 45°. 
     A back surface  624  ( FIG.  15 B ) of the first side portion  606 , which can be the unexposed, or internal surface of the first side portion  606  when the knife  600  is fully assembled, can include a pin  632  ( FIG.  15 A ) and a bearing pad  634  ( FIG.  15 B ). The pin  632  can engage with the locking portion  612  when the knife  600  is in a fully assembled configuration, as described further below. The bearing pad  634  can protrude outward from the back surface  624 , in order to reduce the surface area of contact between the first side portion  606  and the blade  604  when the knife is in a fully assembled configuration, as explained further below. The bearing pad  634  can also be made of a different material than the rest of the first side portion  606 , for example, a relatively lubricous metal material, to reduce friction between the blade  604  and the first side portion  606 . The bearing pad  634  can have a generally semi-circular shape which surrounds the flat-oval opening  620 , and partially surrounds the circular opening  618 , of the engagement element  614 A. In some cases, a washer can be used in place of bearing pad  634 . 
     The second side portion  608  can have an overall shape generally matching that of the first side portion  606 . As best shown in  FIG.  15 A , the second side portion  608  can include three engagement elements  636 A-C protruding outwardly from an internal surface  638  of the second side portion  608 , which can be the unexposed surface of the second side portion  608  when the knife  600  is fully assembled. Second side portion  608  can include more or fewer than three engagement elements  636 , but in many embodiments, the second side portion  608  can have the same number of engagement elements  636  as first side portion  606  has engagement elements  614 . The engagement elements  636  of the second side portion  608  can be configured to engage the engagement elements  614  of the first side portion  606 , as further described below. The positions of the engagement elements  636  on the second side portion  608  can also be configured such that the engagement portions  636  can be aligned with respective circular openings  618  simultaneously. 
     Each of the engagement elements  636 A-C can include a relatively wide base portion  640 , a relatively narrow neck portion  642 , and a relatively wide head portion  644 . In the illustrated embodiment, the neck and head portions  642  and  644  can comprise portions of respective screws which can pass through the respective base portions  640  and be screwed into threaded openings  676  in a main body  646  of the second side portion  608 . As shown, engagement element  636 A can include a washer  648  disposed between the main body  646  of the second side portion  608  and the base portion  640  of the engagement element  636 A. The washer  648  can reduce the surface area of contact between the second side portion  608  and the blade  604  when the knife  600  is in a fully assembled configuration, as explained further below. The washer  648  can also be made of a different material than the rest of the second side portion  608 , for example, a relatively lubricous metal material, to reduce friction between the blade  604  and the second side portion  608 . In some cases, a washer need not be a component of the engagement element  636 A and can be a separate component. 
     As shown, the second side portion  608  can also include a pin  650  protruding outwardly from the internal surface  638  of the second side portion  608 . The pin  650  can engage with the locking portion  612  when the knife  600  is in a fully assembled configuration, as described further below. 
     The liner lock portion  610  can have an overall shape generally matching that of the first and second side portions  606 ,  608 , and can comprise a relatively thin piece of material, such that proximal and distal leaf springs  652 ,  654  can be manipulated by a user relatively easily. The liner lock portion  610  can include four openings  656 A-D, which can be sized and positioned such that the liner lock portion  610  can be positioned adjacent to the second side portion  608  with the engagement elements  636 A-C extending through openings  656 A-C, respectively, and with the pin  650  extending through the opening  656 D. When the knife  600  is in a fully assembled configuration, the distal leaf spring  654  can protect against inadvertent closing of the blade  604  after it has been opened by a user, and the proximal leaf spring  652  can prevent the locking portion  612  from accidentally moving to an unlocked position, as described further below. 
     The locking portion  612  can include a pivot opening  658 , which can be sized to fit over the base portion  640  of the engagement element  636 C such that the locking portion  612  can pivot about the engagement element  636 C, for example, from a locked position when the knife is fully assembled to an unlocked position allowing the knife to be assembled or disassembled. The locking portion  612  can also include a notch  660  which can be positioned to fit over the pin  650  when the pivot opening  658  is fitted over the engagement element  636 C. The notch  660  can have a shape which allows the pin  650  to move through the notch  660  as the locking portion  612  is pivoted about the engagement element  636 C. For example, the notch  660  can include a first end  660 A and a second end  660 B such that the pin  650  is situated at the first end  660 A when the knife  600  is in a fully assembled configuration (and the locking portion  612  is in a locked position, as shown in dashed lines in  FIG.  17   ), and such that the pin  650  is situated at the second end  660 B when the locking portion  612  is in an unlocked position such that the knife can be assembled or disassembled (as shown in solid lines in  FIG.  17   ). The locking portion  612  can also include an opening  662  which can be positioned to receive the pin  632  of the first side portion, as described further below. 
     The locking portion  612  can further include a locking surface  664  which can be situated to engage with a proximal end portion of the proximal leaf spring  652  when the locking portion  612  is in a locked position. The locking portion  612  can also include a manipulation portion  666  extending outwardly from the rear end of the handle which can allow a user to more easily manipulate the locking portion  612  with his or her fingers. 
     The blade  604  can include a pivot opening  668  sized to fit over the base portion  640  of the engagement element  636 A but not over the washer  648 . In this manner, the engagement element  636 A serves as a pivot pin or pivot element for the blade. The blade can also include a first locking surface  670  which can be situated to engage with a distal end portion of the distal leaf spring  654  when the blade  604  is in an open position, and a second locking surface  672  which can be situated to engage with the base portion  640  of the engagement element  636 B when the blade is in the open position. In this way, the distal leaf spring  654  and engagement element  636 B can act to prevent the blade  604  from moving with respect to the handle  602  when the blade is in an open position. Further, the blade can be configured such that the first locking surface  670  is positioned to engage with the base portion  640  of the engagement element  636 B when the blade  604  is in a closed position, such that the blade  604  cannot pivot about the engagement element  636 A to the extent that the blade is exposed outside the handle  602 , e.g., by pivoting beyond the top surface  628 . The blade  604  can also include an extension  674  which can extend outside the handle  602  when the blade  604  is in a closed position, which can allow a user to more easily manipulate and open the blade  604  with his or her fingers. 
     With the various components thus described, assembly and disassembly of the knife  600  will now be explained. To assemble the knife  600 , the second side portion  608  (including the engagement elements  636 ) can be laid on a flat surface with the engagement elements  636  protruding outward from the flat surface. The liner lock portion  610  can then be laid down over the second side portion, with the engagement elements  636  extending through the respective openings in the liner lock portion  610 . The locking portion  612  can then be laid down over the liner lock portion  610  with the pin  650  situated at the second end  660 B of the notch  660  (that is, in the unlocked position shown in  FIG.  16   ). The blade  604  can then be laid down over the liner lock portion such that the engagement element  636 A extends through the pivot opening  668 . The first side portion  606  can then be laid down over the blade  604  and the locking element  612  such that the respective head portions  644  of the engagement elements  636  extend through respective circular openings  618  of the engagement elements  614 . Thus, the head portions  644  can be situated within respective recesses  616  and the neck portions  642  can be situated within respective circular openings  618 . 
     The locking portion  612  can then be pivoted about the engagement portion  636 C from the open (unlocked) position to the closed (locked) position, as indicated by arrow  680  in  FIG.  19   . As the locking portion  612  so pivots, the engagement of the opening  662  of the locking portion  612  and the pin  632  of the first side portion  606  causes the first side portion  606  to rotate slightly about element  636 A and translate distally as indicated by arrow  682  until the first side portion  606  is aligned side-by-side with the second side portion. In this position, the head portions  644  are positioned within respective recesses  616  and the neck portions  642  are positioned within respective flat-oval openings  620 . Thus, the first side portion  606  is restrained against separation from the second side portion  608 , as the head portions  644  are engaged with respective lips  626 . When the locking portion  612  reaches the closed position, the proximal leaf spring  652  engages with the locking surface  664 , restraining the locking portion from motion toward the open position, and the knife  600  is in the fully assembled configuration, as shown in  FIG.  18   . The blade  604  can then be pivoted to the open position, wherein it is locked open by the distal leaf spring  654 . A user can manually depress the distal leaf spring  654  to close the blade  604 . Each lip  626  can be a ramped surface that increases in thickness extending from the opening  618  to the end of the recess  616  opposite the opening  618 . In this way, as the head portion  644  slides against the ramped lip  626 , the frictional contact between the head portion  644  and the lip  626  increases and the spacing between the side portions  606 ,  608  decreases to hold the side portions  606 ,  608 , the blade  604 , and the liner  610  tightly in their assembled state. 
     To disassemble the knife  600 , a user can manually depress the proximal leaf spring  652  and pivot the locking portion  612  toward the unlocked position, causing the first side portion  606  to rotate and translate proximally until the neck portions  642  of the engagement elements  636  are situated within the circular openings  616 , at which point the various components can then be removed from one another laterally. 
       FIGS.  20 - 23    illustrate an alternative embodiment of an easily disassembled folding knife  700 . Knife  700  can include a handle  702  and a blade  704 . The handle  702  can include a first side portion  706 , a second side portion  708 , and a locking button  744 . The first side portion  706  can include a main body  710 , a circular recess  712  formed in an outer surface  714  (i.e., an exposed surface when the knife  700  is fully assembled) of the main body  710 , and a flat-oval shaped opening  716  extending from the recess  712  through the main body  710  to form a lip or ledge  717 . The first side portion  706  can also include a protruding pin  718  extending from an inner surface  720  ( FIG.  23   ) of the main body  710 . The recess  712 , opening  716 , and pin  718  can be located at a distal portion of the first side portion  706 . A proximal portion of the handle  706  can include a locking portion  722  which is offset from the main body  710  in the direction of the inner surface  720 , such as by an intermediate offsetting element  723 . The locking portion  722  can include a circular locking recess  724 . 
     The second side portion  708  can include a main body  726 , an engagement element  728  comprising a relatively wide base portion  730 , relatively narrow neck portion  732 , and a relatively wide head portion  734  having a flat-oval shape matching that of (but being slightly smaller than) the flat-oval opening  716  of the first side portion  706 . The second side portion  708  can also include a semi-circular groove  736  positioned partially around the engagement element  728 . The second side portion  708  can also include a locking portion  738  which is offset from the main body  726  in the direction of an inner surface  740  ( FIG.  23   ) of the main body  726 , such as by an intermediate offsetting element  741 . The locking portion  738  can include a circular locking opening  742 . 
     The blade  704  can include a circular opening  746  sized to fit over the engagement element  728 , a first locking surface  748  situated to engage the pin  718  when the knife  700  is in a fully assembled configuration and the blade  704  is in a closed position, and a second locking surface  750  situated to engage the pin  718  when the knife is in a fully assembled configuration and the blade  704  is in an open position. The blade  704  can also have a shape including an extension  752  which extends from the fully assembled knife  700  when the blade is in both the open and the closed positions, in order to assist a user in opening and/or closing the blade. The locking button  744  can include a relatively wide base  754 , relatively narrow head  756 , and a spring  758  disposed in recess  724  and extending away from the base  754  in a direction away from the head  756 . 
     As shown in  FIG.  21   , the knife  700  can also include a sharpening element  760  coupled to, for example, the inner surface  740  of the second side portion  708 . The sharpening element can include, as examples, a sharpening steel element, or a diamond sharpening element or any suitably abrasive surface to allow a user to sharpen a blade (e.g., blade  704 ) thereon. Any of the knives described herein can include such a sharpening element, e.g., to facilitate sharpening of the blade in the field. Advantageously, this eliminates the need to carry a separate sharpener for sharpening the blade of the knife. If the blade  704  needs sharpening, the knife can easily be disassembled, preferably without the use of any tools and the blade can be sharpened on the sharpening surface  760  of the handle portion  708 . In other embodiments, element  760  can be a removable sharpening element that can be removed from handle portion  708  for use. 
     To assemble the knife  700 , the opening  746  of the blade can be positioned over the engagement element  728  of the second side portion  708 . The flat-oval opening  716  of the first side portion  706  can then be aligned with the flat-oval head portion  734  of the second side portion  708 , and the first side portion can be laid over the second side portion such that the head portion  734  is situated within the recess  712 , the neck portion  732  is situated within the opening  716 , and the pin  718  is situated within the groove  736 , as shown in  FIG.  22   . The button  744  can then be situated such that the spring  758  fits within the circular recess  724 . By depressing the button into the recess  724  (e.g., by manually pressing the button  744  to compress the spring  758 ) and rotating the first side portion  706  such that the locking portion  722  moves toward the locking portion  738  (and the pin  718  moves within the groove  736 ), as indicated by arrow  762  in  FIG.  22   , the first side portion  706  can be locked to the second side portion  708 . That is, first side portion  706  is restrained against motion away from the second side portion by the engagement of the head portion  734  with the lip  717  and by the engagement of the locking portion  738  with the locking portion  722 . 
     Further, by rotating the first side portion until the button  744  is aligned with the circular locking opening  742 , the button can be urged into engagement with the opening  742  by the spring  758 , such that the head  756  is positioned within the opening  742 , and the base  754  is positioned within the recess  724 , as shown in  FIG.  23   , thereby preventing any further relative rotation between the side portions  706 ,  708 . To disassemble the knife  700 , the button can then be depressed (e.g., manually) until its head  756  is no longer situated within the opening  742 , the first side portion  706  can be rotated to separate the locking portions  722 ,  738  and align the head portion  734  with the opening  718 , and the components can then be removed from one another laterally. In some cases, the knife  700  incorporates washers or similar components, as described above, e.g., with respect to knife  600 . In some cases, the knife  700  incorporates a liner lock or other similar component, as described above, e.g., with respect to knife  600 . In some embodiments, the base  754  of the button  744  can be configured to be retained within the recess  724  when the first side portion  706  is separated from the second side portion  708 . 
       FIGS.  24 - 28    illustrate an alternative embodiment of an easily disassembled folding knife  800 . Knife  800  can include a handle  802  and a blade  804 . The handle  802  can include a first side portion  806  and a second side portion  808 . The first side portion  806  can include a main body  810 , two circular recesses  812 ,  814  formed in an outer surface (i.e., an exposed surface when the knife  800  is fully assembled) of the main body  810 , and two respective flat-oval shaped openings  818 ,  820  extending from the recesses  812 ,  814  through the main body  810  to form respective lips or ledges  822 ,  824 . The first side portion  806  can also include a protruding pin  826  extending from an inner surface of the main body  810 . The recess  812 , opening  818 , and pin  826  can be located at a distal portion of the first side portion  806 , while the recess  814  and opening  820  can be located at a proximal portion of the first side portion  806 . 
     The second side portion  808  can include a main body  830 , an engagement element  832  comprising a relatively wide base portion  834 , relatively narrow neck portion  836 , and a relatively wide head portion  838  having a flat-oval shape matching that of (but being slightly smaller than) the flat-oval opening  818  of the first side portion  806 . The second side portion  808  can also include a divot  864  which can receive an end of the pin  826  when the knife  800  is fully assembled. The second side portion  808  can also include a locking portion  840  which includes an actuating arm  842  and a retaining element  843  mounted to the arm  842 . The retaining element  843  comprises a relatively narrow neck portion  844  and a relatively wide head portion  846  having a flat-oval shape matching that (but being slightly smaller than) the flat-oval opening  820  of the first side portion  806 . The actuating arm  842  and retaining element  843  can be coupled to one another such that rotation of the arm  842  causes rotation of the retaining element  843 . The second side portion  808  can also include a pair of pins  848  which can prevent the actuating arm  842  from being rotated too far into the handle  802  when the knife  800  is fully assembled. 
     As shown, the flat-oval openings  818 ,  820  of the first side portion  806  can be oriented in the same direction. That is, the flat sides of the flat-oval openings  818 ,  820 , can be generally parallel to one another. As also shown, the flat-oval head portion  838  can be oriented such that the flat sides of the head portion  838  are offset angularly from the flat sides of the opening  818  when the knife  800  is fully assembled, as shown in  FIG.  24   . Further, the head portion  846  of retaining element  843  can be oriented such that the flat sides of the head portion  846  are offset angularly from the flat sides of the opening  820  when the knife  800  is fully assembled (as shown, they are offset by about 90° when the knife  800  is fully assembled, but various angular offsets are suitable). 
     The first and second side portions  806 ,  808 , of the knife  800  can include divots  858  and the actuating arm  842  can include gripping elements  860  (e.g., a nail-nick) aligned with the divots  858 , in order to further facilitate the manual operation (e.g., rotation) of the actuation arm  842 . The blade  804  can include a circular opening  850  sized to fit over the engagement element  832 , a first locking surface  852  situated to engage the pin  826  when the knife  800  is in a fully assembled configuration and the blade  804  is in a closed position, and a second locking surface  854  situated to engage the pin  826  when the knife is in a fully assembled configuration and the blade  804  is in an open position. The blade  804  can also have a shape including an extension  856  which extends from the fully assembled knife  800  when the blade is in both the open and the closed positions, in order to assist a user in opening and/or closing the blade. 
     To assemble the knife  800 , the opening  850  of the blade can be positioned over the engagement element  832  of the second side portion  808 , as shown in  FIG.  28   . The flat-oval opening  818  of the first side portion  806  can then be aligned with the flat-oval head portion  838  of the second side portion  808 , and the first side portion  806  can be laid over the second side portion such that the head portion  838  is situated within the recess  812 , and the neck portion  836  is situated within the opening  818 , as shown in  FIG.  27   . The locking portion  840  can then be rotated such that the opening  820  will be aligned with the head portion  846  when the first side portion  806  is rotated to bring the opening  820  to the head portion  846 . The first side portion  806  can then be rotated about engagement element  832  such that the opening  820  moves toward the locking portion  840  and head portion  846 . Once the first side portion  806  has been rotated so the opening  820  overlays the head portion  846 , the opening  820  can be seated on the locking portion  840  such that the neck  844  is situated within the opening  820  and the head  846  is situated within the recess  814 , as shown in  FIG.  25   . The locking portion  840  can then be rotated such that the head  846  is no longer aligned with the opening  820 , such as by manual operation (e.g., rotation) of the actuating arm  842  to the closed or locked position shown in  FIG.  24   . The first side portion  806  thus can be restrained against motion away from the second side portion  808  by the engagement of the head portion  838  by the lip  822  and by the engagement of the head  846  by the lip  824 . 
     To disassemble the knife  800 , the locking portion  840  can be rotated to the open or unlocked position to align the head  846  with the opening  820 . The first side portion  806  can then be lifted off the locking portion  840  and rotated to align the opening  818  with the head portion  838 . The components of the knife  800  can then be removed from one another laterally. In some cases, the knife  800  incorporates washers  862  or similar components, as described above, e.g., with respect to knife  600 . In some cases, the knife  800  incorporates a liner lock or other similar component, as described above, e.g., with respect to knife  600 . In addition, one or both of lips  822 ,  824  can comprise a ramped surface with increasing thickness that contacts a respective head portion  838 ,  846 . As the side portion  806  is rotated from the position shown in  FIG.  27    to the position shown in  FIG.  24   , frictional contact between the ramped surface and the respective head portion increases and the lateral spacing between the side portions  806 ,  808  decreases, thereby tightly holding the side portions  806 ,  808 , and the blade  804  together in the assembled state. 
       FIGS.  29 - 35    illustrate an alternative embodiment of an easily disassembled folding knife  900 . Knife  900  can include a handle  902  and a blade  904 . The handle  902  can include a first side portion  906  and a second side portion  908 . The first side portion  906  can include a main body  910  and two recesses  912 ,  914  formed in an outer surface  916  (i.e., an exposed surface when the knife  900  is fully assembled) of the main body  910 . As best shown in  FIG.  35   , the recesses  912 ,  914  can each have shapes resembling the shape of a keyhole, or include a circle-shaped portion  918  with a fan-shaped portion  920  extending away from the circle-shaped portion  918 . The first side portion  906  can further include two circular openings  922 ,  924  extending from the centers of respective circle-shaped portions  918  through the main body  910 . 
     The first side portion  906  can also include two rotatable locking or retaining elements, or locks  926 ,  928  situated within respective recesses  912 ,  914 . The locks  926 ,  928  can have shapes comprising circles with circular recesses  927 ,  929  at their centers and hexagonal openings  930 ,  932  at the centers of the circular recesses  927 ,  929 . The locks can also have respective actuators or levers  934 ,  936  extending away from the circle-shaped portions. The actuators  934 ,  936  can be positioned within the respective fan-shaped portions  920  of the recesses  912 ,  914  such that a user can move the actuator from one side of the fan-shaped portion  920  to the other side of the fan-shaped portion  920  to cause the hexagonal openings  930 ,  932  to rotate. The first side portion  906  can also include several screws  938  screwed into the main body  910  such that the heads of the screws overlap the recesses  912 ,  914 , and locks  926 ,  928 , to retain the locks  926 ,  928  within the recesses  912 ,  914 . 
     The second side portion  908  can include a main body  940 , a spacer  942 , a distal engagement portion  944 , a proximal engagement portion  946 , and a pin  948 . The distal engagement portion  944  can include a relatively wide base portion  950 , a relatively narrow neck portion  952 , and a relatively wide head  954 . The proximal engagement portion  946  can similarly include a relatively wide base portion  956 , a relatively narrow neck  958 , and a relatively wide head  960 . The heads  954 ,  960  can have shapes matching that of, but being slightly smaller than, the hexagonal openings  930 ,  932 . In some cases, the rotatable locks  926 ,  928  can be fabricated from the same material (e.g., steel) as the heads  954 ,  960  so that the head portions  954 ,  960  can easily slide through the hexagonal openings  930 ,  932  in the locks  926 ,  928 . 
     The spacer  942  can be coupled to the main body  940 , for example by an adhesive, by screws  962  as shown, or by various other suitable means. The distal engagement portion  944  can be seated within a recess  943  in the main body  940  and coupled thereto by a screw  945 , or by various other suitable means. The proximal engagement portion  946  can be seated within a recess  947  in the spacer  942  and coupled thereto by a screw  949 , or by various other suitable means. The pin  948  can be situated to engage the blade (described below) to prevent it from pivoting farther than desired. 
     The blade  904  can include a circular opening  964  sized to fit over the distal engagement portion  944  and a semi-circular slot  966  positioned with respect to the opening  964  to fit over the pin  948  when the opening  964  is fitted over the engagement portion  944 . The blade  904  can also include an extension  968  which can extend free of the handle  902  when the knife  900  is fully assembled and the blade is in either an open or a closed position, in order to assist a user in opening and/or closing the blade  904 . 
     As shown in  FIG.  35   , the knife  900  can also include a recessed compartment  974  housed within the second side portion  908 . The compartment  974  can allow a user of the knife  900  to store various items in the handle  906  of the knife  900 , for example, other blades or tools, flint and steel, blade sharpeners, matches, medication, or any other sufficiently small items the user may want to have available in the field. Any of the knives described herein can include such an internal compartment, e.g., to facilitate storage and concealing of small items in the field. The recessed compartment  974  can be covered by a lid  976 , which can be pivotally connected to the inside surface of the handle portion  908 . 
     To assemble the knife  900 , the opening  964  of the blade  904  can be positioned over the engagement element  944  such that the pin  948  is positioned within the slot  966 . The locks  926 ,  928  can then be actuated such that the hexagonal openings  930 ,  932  are generally aligned with the heads  954 ,  960 . The first side portion  906  can then be laid down on the second side portion  908  such that the engagement portions  944 ,  946  extend through the openings  922 ,  924 ,  930 ,  932  such that the necks  952 ,  958  are situated within the hexagonal openings  930 ,  932 , and such that the heads  954 ,  960  are situated within the circular recesses  927 ,  929 . The locks  926 ,  928  can then be actuated (pivoted) such that the hexagonal openings  930 ,  932  are no longer aligned with the heads  954 ,  960 , thereby locking the first side portion  906  to the second side portion  908 , in a manner similar to that described above. In some cases, the head portions  954 ,  960  can comprise a ramped surface with variable thickness that contacts the respective locks  926 ,  928 , and the surfaces of the locks  926 ,  928  which contact the head portions  954 ,  960 , can comprise complementarily ramped surfaces with variable thickness. Thus, as the locks  926 ,  928  are rotated from an unlocked to a locked position, frictional contact between the head portions  954 ,  960 , and the locks  926 ,  928  increases and the lateral spacing between the side portions  906 ,  908  decreases, thereby tightly holding the side portions and the blade together in the assembled state. 
     To disassemble the knife  900 , the locks  926 ,  928  can be actuated such that the hexagonal openings  930 ,  932  are aligned with the heads  954 ,  960 , and the components of the knife  900  can then be removed from one another laterally. In some cases, the knife  900  incorporates washers  970  or similar components, as described above, e.g., with respect to knife  600 . In some cases, the knife  900  incorporates a liner lock or other similar component, as described above, e.g., with respect to knife  600 . 
       FIG.  36    shows one embodiment of the second side portion  908  including a recess  978  formed in the second side portion  908  and a secondary tool element  980  pivotally coupled to the second side portion  908  by pivot element  982 . In particular embodiments, the recess  978  can be formed on the inside surface of the side portion  908 , although it can be formed on the outside surface of the side portion  908  in other embodiments. In this embodiment of the second side portion  908 , the secondary tool  980  can pivot with respect to the second side portion from a closed position, in which the tool  980  is situated within the recess  978 , and an open position, in which the tool  980  can be used. Thus, when a user is using the blade  904  of the knife  900 , or when a user is not using the knife  900 , the secondary tool  980  can be hidden within the knife  900 . When a user desires to use the secondary tool  980 , the tool  980  can be pivoted about element  982  to an open position for use. If desired, the side portion  908  can be removed from the knife, and the side portion  908  and tool element  980  can be used as a separate tool. In various embodiments, the tool  980  can comprise a blade, a screwdriver, a can opener, a sharpener for sharpening the blade  904 , a nail file, or any other suitable tool known in the art. 
     In any of the embodiments described herein, any of various mechanisms can be used to lock the blade of a folding knife in the open and the closed positions, and a thumbstud can be used to stop the rotation of the blade when received in the handle. Further, in any of the embodiments described herein, a knife can include one or more dowels or thumb-actuated screws  984  ( FIG.  31   ) each of which extends through one side portion  906  and is tightened into a threaded opening in the other side portion  908 . The screw  984  allows a user to tighten the first and second side portions of a handle laterally toward one another using manual pressure without the use of tools. Further, in any of the embodiments described herein, a bearing system such as is described in U.S. Pat. App. Pub. No. 2012/0234142 can be incorporated into the knife in order to reduce friction forces exerted against the blade of the knife, for example, as the blade is opened or as the blade is closed. In any of the embodiments described herein, a knife can be provided in a kit with a plurality of blades or other tools. Because the folding knives described herein are more readily disassembled and re-assembled than other known knives, any of the blades in the kit can easily be installed in the knife, depending on the particular functionality desired. In any of the embodiments described herein, a knife can be provided with a clip secured to the handle portion so that the knife can be clipped onto, for example, a user&#39;s belt or pocket. 
     Further still, except where structurally impossible, any of the features described herein can be used in combination with any other feature described herein. For example, a folding knife can include a first side portion having locking elements formed integrally, such as in knife  200 , and a second side portion having a recess and cavity for receiving the locking elements, such as in knife  300 . Similarly, a folding knife can include a first side portion and structurally distinct locking elements which together can form an assembly, such as in knife  300 , and a second side portion having an opening extending therethrough, such as in knife  200 . In another embodiment, a folding knife can comprise the locking portion  840  of the embodiment of  FIGS.  24 - 28    to retain the rear ends of handle side portions together and the locking element  926  of the embodiment of  FIGS.  29 - 35    to retain the forward ends of the handle side portions together. 
     The embodiments disclosed herein provide advantages over prior folding knives, including prior folding knives having removable blades. For example, some of the knives disclosed herein have a simple construction which can increase reliability of the knife and simplify the process of removing or replacing a blade. In the illustrated embodiments, the handle can be disassembled and the blade can be removed or replaced by hand, without using any tools, and preferably without removing any small parts, thereby reducing or eliminating the chance of losing a part of the knife. 
     For purposes of this description, certain aspects, advantages, and novel features of the embodiments of this disclosure are described herein. The disclosed methods, apparatuses, and systems should not be construed as limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The methods, apparatuses, and systems are not limited to any specific aspect or feature or combination thereof, nor do the disclosed embodiments require that any one or more specific advantages be present or problems be solved. 
     Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed methods can be used in conjunction with other methods. As used herein, the terms “a”, “an” and “at least one” encompass one or more of the specified element. That is, if two of a particular element are present, one of these elements is also present and thus “an” element is present. The terms “a plurality of” and “plural” mean two or more of the specified element. 
     As used herein, the term “and/or” used between the last two of a list of elements means any one or more of the listed elements. For example, the phrase “A, B, and/or C” means “A,” “B,” “C,” “A and B,” “A and C,” “B and C” or “A, B and C.” 
     As used herein, the term “coupled” generally means physically coupled or linked and does not exclude the presence of intermediate elements between the coupled items absent specific contrary language. 
     In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. I therefore claim as my invention all that comes within the scope and spirit of these claims.