This is a derivative of both thing:1088 and thing:1082, with inspiration from the improved snap from thing:5322. However the pattern was totally redrawn from basic principles to make it fully parametric, rather than relying on the original dxf outlines.

The point of this design is to take full advantages of the abilities of a 3d printer, rather than just converting a laser cut design into a 3d part with difficult overhangs. The triangle should end up fully trapped inside the case.

Note that from a top view, it may appear the triangle and case overlap, but from a per-layer perspective, they are separated by the tolerance, and do not actually touch.

Due to the large square area, this part may warp without a heated build platform. The second verison is identical to the first, except that I have added ears that seem to help significantly (with my sample population of one) to prevent warping. (Thanks for the idea: http://blog.makerbot.com/2011/02/25/mouse-ears-defeat-corner-curling-monster/ )

The parts should come out separated, but may be initially connected by raft and strings. Carefully cut these away so the triangle rolls smoothly in the case. Since all interior faces are 45 degree angles, it should be easy to slip a knife between the parts to do any necessary cleaning.

Note that skeinforge 35 and previous do not slice this object correctly (although build quality suffers only slightly). This was fixed somewhere between skeinforge 35 and 40.