Called “dead” because there are no springs to operate the bolt. It is only operated manually with a key or a thumb turn from the inside.
The bolt locks the door to the frame and helps prevent someone from prying the door open.
The throw is the length the bolt is extended from the lock housing.The industry standard is a 1” throw.
Locks are designed to fit specific size holes and backsets. Backset refers to the distance between the edge of the door and the center of the handle.
A single-cylinder deadbolt is operated with a key from the outside and with a turn button on the inside. It is used mostly with solid metal or wood doors.
A double-cylinder deadbolt is operated with a key on both the inside and outside. It is best used on a door with glass in or around them as the style prevents someone from breaking the glass, reaching in and unlocking the door.
Double-cylinder deadbolts can pose a danger during an emergency. If the key is missing or not readily available, people could be trapped inside a locked house. In some areas, codes may not permit this style of deadbolt.