The windows of my house have these track locks on the sides that when released allow my window to fold into the house for easy cleaning. Problem is that they are plastic and break easily. The only way to get replacement ones is to have a windows installer company come out, the manufacturer won't sell them to the public. So the very first thing I created with my Da Vinci 2.0 Duo 3D printer was replacement Track Locks.Download STL, it includes a Left and Right Track Lock. Every window manufacturer that has fold out windows use a variation of these devices. Feel free to edit this STL to fit your specific windows. Print out the STL and assemble by fitting the smaller piece that looks like it has two flat legs into the bigger piece so the tall piece goes thru the opening (see picture).