Provides double protection. Sliding deadbolt with mortise strike for door jamb assures positive locking action while chain door fastener allows door to open 4-1/2" for identification or ventilation. Made of extruded brass with twist link chain of case-hardened steel. Packed 1 unit in visual dome pack complete with mortise, strike, and 1 x 6 sheet metal screws. Extruded brass.