Deadbolt

Lore & Background

The deadbolt is a lock mechanism morticed into a wooden door, with a bolt that extends into the door frame. Unlike spring bolt locks, which use a spring to hold the bolt and can be retracted by applying force to the bolt itself, a deadbolt can only be opened by a key or handle. This design makes the door more resistant to forced entry and entry without the correct key. A variant, the vertical deadbolt, was invented by Samuel Segal to resist jimmying, where an intruder uses a crowbar between the door and jamb.

Reader's Guide

The deadbolt is significant for its enhanced security compared to spring bolt locks, as it cannot be retracted by direct force on the bolt. Its design forces reliance on a key or handle, reducing the risk of unauthorized entry. The double cylinder variant, which requires a key on both sides, prevents unlocking via a broken interior window but introduces a fire safety hazard: occupants may be trapped if the key is not readily available. This has led to fire safety codes restricting such locks on exits. Single cylinder deadbolts, with an interior twist knob, avoid this issue and are common on fire exits. The vertical deadbolt variant specifically counters jimmying. Overall, the deadbolt remains a standard complement to spring bolt locks on building entry doors, balancing security and safety considerations.

Did You Know?

• A deadbolt can only be opened by a key or handle, unlike a spring bolt lock which can be retracted by applying force to the bolt itself.
• Double cylinder deadlocks require a key on both sides and may be banned in some areas due to fire safety regulations.
• The vertical deadbolt, invented by Samuel Segal, resists jimmying with a crowbar between the door and jamb.
• Some fire departments suggest placing the key for a double cylinder deadlock on a nail near the door at floor level, where the cleanest air is during a fire.