I am rtying to locate parts for the Crestopane Windows. I am working on windows made in 1981 that use a vinyl side track with a metal clip connected to a long spring anchred to the top of the track. The metal clip catches in a metal bracket attached to the side of the window after the windows are put in the tracks. these windows are removable by pressing hard to one side which causes the track to flex inward so the opposite side of the window can be lifted out of the track. I've not had much luck on identifying the "clip" part name or where I can find replacements. The windows themselves are in excellent condition.