I'm having a problem properly defining a mate.. I'm constructing a bi-fold door of extruded material.. Each door is an assembly, essentially it's 4 parts all mated to form a rectangle. The hinge is 2 parts turned into an assembly - and that hinge is mated by the top of the hinge (to align it), and the holes are mated concentric. I then have a larger assembly with the doors and a hinge. I have the back of hte hinge mated to the surface of the door; and each top plane of the doors is mated coincident to keep them lined up. I have 1 door fixed. When I try and rotate the floating door - it won't swivel. This is the first time I'm really trying this, so what am I missing? I reviewed the crank assembly sample and it doesn't seem to offer me any pointers - other than it obviously works :)