Spring Latch Locks: A popular and convenient lock that snaps closed whenever the bevelled latch seats into a striker plate is the spring-latch lock. However, this lock can be easily forced by inserting through the door frame a thin blade or stiff plastic between the latch and the strike plate. Thus, a spring lock should always be augmented by a second lock of a different type.
Dead Bolt Locks: The dead bolt lock features a solid, rectangular latch that forms a bolt between the door frame and the door itself. This lock is difficult to force or jimmy and is a good choice as an auxiliary to any other key lock. It’s available for either key operation or manual interior knob.
Barrel-Type Bolt: A barrel-type bolt serves the same function as the dead-bolt lock but is restricted to manual, interior operation only. It may be used with an inxpensive night-latch, and it is difficult to force if it’s well made and installed properly.
Chain Locks: Used as a supplementary interior lock, the welded chain offers a valuable security feature. It permits the user to open a door partially to exchange letters, messages, or small parcels without completely unlocking the door. For proper mounting, the slide should be installed just above and slanting toward the chain.screw sizes chart