bolt which is not actuated by a spring. When locked the bolt cannot be returned by end pressure.
An auxiliary lock operated independently of the ordinary spring mortise lock, the bolt of which cannot be moved except by the use of a key or an inside knob. A double cylinder dead bolt is one that can be operated only by a key on either side of the door.
A locking device that can be activated only with a key or thumb turn. Unlike a latch which has a beveled tongue, dead bolts have square ends.