This is a heavy-duty Prime-Line S 4033 Window Security Lock has a tamper-resistant Allen head set screw and included wrench to securely lock windows and prevent accidental opening by a child. For use on metal a horizontal sliding window. The design of this child safety lock is manufactured to fit on older style, metal framed windows, usually of single pane glass with a maximum frame lip or fin thickness of 1/4 inch. This tamper resistant lock can be used to securely lock windows in closed or ventilating positions. Made of extruded aluminum in a black finish, this is strong, durable, and built to last.