A security device for a sliding door or sliding window
assembly comprising a base plate and a removably
interlocking stop member. The base plate is securely fastened to the floor or
window sill, respectively, in close proximity and along the path of movement of a sliding door or sliding window, by means of a plurality of openings for receiving screws. The stop member, while engagingly disposed in the interlocked, in use position, prevents the sliding door or sliding window from opening at all or past a predetermined point. The base plate and stop member are each formed having an
interlocking means element, adapted to receive, matingly, the others
interlocking means element. The stop member features a blocking element, which projects into the path of the sliding door or sliding window, while in the in use position. Removing the stop member allows normal movement of the sliding door or sliding window.