I have aluminum Amsco 703 windows, single hung, 30 yrs old that are in good condition except for these black clips that break occasionally. The main windows are double pane and there is a separate up/down sliding inner window (effectively triple pane) that has a clip on the side of the lower inner window. This clip prevents the window from moving incorrectly in the track when lifted. This black clip can be rotated so that it allows the window to be removed from the track. Do you have these clips?
Thank you,
Dale