Replace broken, old, or unsightly door locks with the Defender Security S 4003 Sliding Door Patio Lock. This twist-in lock is constructed of a Zamak cast housing, an aluminum bolt, and it comes in a black painted finish. This secondary lock provides increased security when ventilating or securing your sliding patio door, as it prevents sliding and lifting of active panel. This lock is also compatible with some horizontal sliding windows. It features a 1/2 inch reach with an overall height of 11/16 inch and 1-9/16 inch mounting hole centers. The lock mounts onto the lower back-edge of the sliding panel, and the bolt locks into a 1/4 inch hole that must be carefully drilled into the fixed panel's bottom rail. For further dimensional information, please see the line drawing.