A 5 lever British Standard BS3621 mortice deadlock is a lock which is required by insurance companies to be fitted to all external wooden doors. It is morticed, cut into, the edge of the door and is operated by a key from both sides. The deadbolt, which is thrown by the key, engages into a strike plate which is fitted to the door frame. There are certain features a deadlock has to have to be a British Standard deadlock. They must have at least 5 levers, levers are what the key has to move up in order for you to throw the bolt, lock or unlock the lock. There must also be a curtain, bolt thrower, which protects the levers from being manipulated and the lock being picked open. The bolt must have some form of hardening, some locks have hardened pins running through the bolt whilst some manufacturers make the entire bolt hardened, meaning you can not cut through the bolt with a hacksaw. The bolt which is thrown by the key and engages into the strike plate must be of a certain size and length. A deadlock must also have hardened plates attached to the body of the deadlock to prevent anyone drilling through the door into the lock with a standard drill bit. Lastly the strike plate, which is fitted to the door frame and the bolt engages into, must be a boxed strike plate and of a certain size.
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