Abstract: A locking apparatus for sliding metal casement windows, doors and the like, the apparatus being adapted to be lockably secured within the lower or upper track portion of the window casement so as to prevent the slidable window from being laterally or vertically moved therein, the locking apparatus comprising a body member having a substantially rectangular configuration defined by front and rear walls, and top and bottom wall members, a longitudinal opening being provided between the front wall and the bottom wall, and the opening being arranged to receive the outer track wall of the casement, whereby the outer track wall is clamped between the front wall and a locking cam member which is rotatably mounted between the top and bottom walls of the body member, the cam including an eccentrically positioned shaft adapted to receive a knob for locking and unlocking the apparatus.