Patio Door Locks: The versatile surface mounted deadbolt. "Gets-A-Hold, Won't-Let-Go". Ideal for: sliding patio doors, sliding windows, swinging doors, double doors, french doors, plus many more. Can be used on narrow stile doors and frames with a frame width of only 1 5/8". Lock housing will accept a standard 1 1/8" mortise cylinder (not included) enabling it to be keyed to other locks in a system. Mounts at top or bottom of door or both.