Prime-Line Products U 9812 Sliding Window Lock, Fits on 1/4 in. Max Fin, Aluminum, White, Tamper Resistant (Pack of 2) Used on vertical and horizontal sliding windows as a secondary tamper resistant window lock For use on 1/4 in. max. thick fins White painted finish Extruded aluminum construction with tamper resistant Allen head set screw Note: This item will not work on windows with lips or fins wider/thicker than 1/4 in.