Defender Security S 4014 Snap-On Vent Lock, 1-3/4 in., Steel, Aluminum Finish, Qty. 2 Used on older metal-framed horizontal sliding windows; 3/16 in. rail thickness Fits on 3/16 in. max. rail thickness. Measures 1-3/4 in. wide x 3/8 in. tall. Aluminum colored finish Stamped steel construction This item's "Snap-On" feature requires no fasteners for installation