Why Is It Called a “Deadbolt”?

For some people, securing their residence can mean having a very large, very vocal dog on patrol. For others, it can mean a firearm. But for the majority, it means throwing a deadbolt on an entry door. With a clunk, it provides both a physical barrier to unwanted visitors as well as a psychological reassurance. No lock is impenetrable, but a deadbolt can at least discourage or slow down the potential of a break-in.

But why is it called a “deadbolt”?

1. Why a Deadbolt Lock is Known as a Deadbolt
2. Single Cylinder vs. Double Cylinder Deadbolt
3. Deadbolt vs. Deadlatch
4. Deadbolt vs. Renter’s Bolt
5. Deadbolts for Security

Why a Deadbolt Lock is Known as a Deadbolt

According to the Oxford English Dictionary, deadbolt first appeared in print in 1808. It’s defined by the OED as “a bolt in a lock that is engaged by means of a key, knob, or (later) electronic device, rather than by a spring action.”

This is the key—no pun intended—to differentiating deadbolts from other types of locks. Think of a doorknob, which has a latch that slides into the recessed portion of the door frame. The latch is spring-loaded, which means it can be physically manipulated by someone looking to force it back into the door. Someone can loid, or jimmy, the lock using a thin strip of material like a credit card.

A deadbolt, on the other hand, cannot be moved unless the lock cylinder is turned. The bolt is “dead,” or immobile, instead of being forced out by a spring.

A good way to think of the difference is to imagine two locks sitting out on a table. You could use your finger to press a spring-loaded latch into the mechanism. But the same isn’t true of a deadbolt. To have the bolt retreat back inside the lock, you’d have to manually turn the cylinder, either with a key on the outside or a manual knob, known as a thumb turn, on the inside.

But not all deadbolts function this way.

Single Cylinder vs. Double Cylinder Deadbolt

A single cylinder deadbolt has keyed entry on the exterior and a thumb turn indoors. A double cylinder deadbolt has two keyed latches, one on both the interior and exterior faces of the lock. This means a key, not a thumb turn, must be used to lock or unlock the deadbolt from inside. This type of lock is also known as a deadlock.

The main benefit of a deadlock is when there are glass panels or windows within arm’s distance of the lock. An intruder could, in theory, smash the glass and reach in to use the thumb turn on a single cylinder deadbolt, gaining entry. But smashing the glass and reaching the lock wouldn’t do them much good on a double cylinder deadbolt: They’d still need the key to turn the bolt.

Double cylinder locks have their detractors. If the lock is engaged while a property is occupied, that means someone would need a key to open the door. In the event of an emergency like a fire, not having the key or delaying exit could mean being trapped.

Deadbolt vs. Deadlatch

A deadlatch functions in a manner similar to a deadbolt, with one big difference: The lock has a beveled edge on a spring, meaning it can be engaged by shutting the door. This is a bit of a hybrid lock, offering some—but not all—the advantages of a deadbolt with some of the conveniences of a conventional spring-loaded lock.

Different Kinds of Deadbolts and How They Work

Deadbolt vs. Renter’s Bolt

There is no keyed entry on the exterior of a renter’s bolt, meaning it cannot be engaged, disengaged, or picked from outside. The bolt, which is also known as a one-sided or single-sided deadbolt, either has a blank exterior hardware face or doesn’t go completely through the door. This makes unauthorized entry harder, but it also means the security of the deadbolt can only be utilized when an occupant is home. A renter’s bolt might be used in an entryway that doesn’t see as much traffic, like a patio or garage door. If it’s used on a primary door, a second locking mechanism would have to be utilized.

Deadbolts for Security

In most cases, having a deadbolt installed on a door is going to offer superior protection against entry than other types of locks. But other factors—like door material—matter, as well. Solid wood or steel clad doors are sturdier than others. But if someone is versed in picking locks, the type doesn’t really matter. (One alternative is a smart lock, which requires a code for keyless entry.)

One thing most security experts agree on is that a deadbolt should be paired with a quality strike plate, or a run of metal that reinforces the doorjamb around the deadbolt. In simple terms, it prevents burglars from brute-forcing their way through the door by kicking it in. It’s certainly possible to force an engaged deadbolt through the wood jamb—but with a strike plate, the bolt will meet metal instead. Using longer screws to secure the strike plate will make forced entry harder, and so will a plate that runs the vertical length of the door.

Deadbolts are just one component of home security. Having cameras, motion lights, and other deterrents can help discourage potential burglars from trying to gain access to a property. Given enough time and opportunity, pretty much any lock can be defeated—the trick is to make it hard enough that someone wouldn’t even bother trying.

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