A deadbolt is a security device that is installed on a door to prevent unwanted intrusion. Home security is a prime concern for most homeowners, and a deadbolt lock can provide a good amount of protection from trespassers. The bolt cannot be pried open, as with a spring-loaded lock.
Deadbolts are also called deadlocks. There are two basic designs, the double cylinder and the single cylinder. The double cylinder bolt can be locked from either side of the door with a key. The single cylinder bolt uses keyed entry outside, but needs no key to open from inside the room. The double deadbolt cylinder is more secure, but the single cylinder provides a convenient and safe way to exit without a key.
There are several different styles of bolt locks, each made for a specific function. A style often seen in public buildings is the exit-only latch, commonly used to provide a safe fire exit. When entering from outside, a key is required; however, pressing a bar or handset on the inside of the door causes it to swing open without a key.
A deadbolt commonly used in schools is referred to as the classroom style deadlock. It can be locked from either side, but only with a key. This protects the key holder from being locked out of the room by a precocious student. A thumbturn on the inside of the lock allows the class to exit quickly in case of emergency.
There is also an exit-only door lock called the thumbturn-only that is used strictly for quick egress. Keys are not needed as there is no unlocking mechanism on the outside of the door. Another style is the vertical deadbolt, which offers solid security at the top of a door with either a key or thumbturn mechanism.
One of the most secure deadbolt styles of all is keyless entry locksets, which are commonly found in the doors of motel rooms and professional buildings. Keyless deadlocks operate via a numbered keypad or a card swipe system. A lost entry card presents much less of a problem than a lost key. The door is electronically secured, so the code can be changed as often as desired. The issuer has complete access control, and a history of each use is recorded for further safety.
Door locks have evolved a long way since the first wooden locks of antiquity. Burglars and other home invaders have become more sophisticated, too. Of course, there are more complex and expensive home security systems available, but a simple deadbolt lock is still an effective crime deterrent.