Common Types
A deadlock, if it is cylinder operated, may be either single cylinder or double cylinder. A single cylinder deadlock will accept a key on one side of the lock, but is operated by a twist knob on the other side. Double cylinder locks will accept a key on both sides and therefore do not require (and often do not have) any twist knob. This prevents unwanted unlocking of the door by forced access to the interior twist knob (via a nearby window, for example). Some lock manufacturers also have a "lockable" knob: there a key is always needed on one side (usually external), and a twist knob can be used on the other (internal), unless a button has been pressed, in which case a key is also needed on the (internal) side.
A variant of the standard deadbolt is the vertical deadbolt, invented by Samuel Segal. Vertical deadbolts resist jimmying, in which an intruder inserts a pry bar between the door and the jamb and attempts to pry the bolt out of the door.
Other types of deadbolts include:
- Single Cylinder with removable thumb-turn
- Classroom Function (thumb-turn only unlocks door)
- Exit Only Function (no external cylinder)
- Push-button Deadbolt (mechanical or electrical)
Read more about this topic: Dead Bolt
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