Dead bolt

A deadbolt or deadlock is a type of lock morticed into a wooden door. Then, using a key from either side of the door, a bolt is thrown into the door frame, thus securing the door. It is distinct from a spring bolt lock because a deadbolt can only be opened by a key or handle. The more common spring bolt lock uses a spring to hold the bolt in place, allowing retraction by applying force to the bolt itself. A deadbolt can therefore make a door more resistant to entry without the correct key, as well as make the door more resistant to forced entry. A deadbolt is often used to complement a spring-bolt lock on an entry door to a building.