This refers to a system in which a set of locks are keyed different, and yet can all be operated using a single key as well. An example would be a set of apartments. Each tenant has a key to his/her own unit which does not work the others. The landlord, however, carries a single master key that operates all units. Office buildings, retail stores, schools, hospitals and churches all utilize master keys systems. Only a professional locksmith can design, implement and maintain a masterkey system properly! See also change key and submaster key.Master key (for a vehicle)
This refers to the key that operates all locks on the vehicle, including the ignition, doors, trunk and glove box and/or consoles. See also valet key.Mortise Lock
This refers to a lock that is installed by carving a rectangular cut-out from the edge of the door. Mortise locks are still made today, but were far more common before the 1950's when cylindrical locks became common. Old “skeleton key” door locks are usually mortise locks, as are residential and commercial locks in which the latch and deadbolt are operated by a single keyhole. (If the keyhole is above or below the knob or lever handle--not built into the handle--you probably have a mortise lock). See also cylindrical lock and rim lock.