Abstract: A window lock for double-hung windows utilizing extension elements joined to each separate window and telescopically mated one with the other with a latch assembly on one element and longitudinally spaced catches on the other element whereby the windows are held in closed or in alternate relative positions providing varied window openings. Mountings facilitate installation and provide for out-of-way pivotted storage. The latch may be retained in a retracted position to facilitate adjusting movements of the windows and telescoping elements.