Deadbolt - Exterior Door Security Lock Guide at Home

A deadbolt is a door lock with a solid metal bolt that extends deep into the frame to provide stronger security than a spring-latch lock.

Deadbolt diagram — labeled parts, dimensions, and installation context

What It Is

A deadbolt is the primary locking device on many exterior doors. Unlike the latch in a standard knob or lever set, the bolt does not rely on a spring to stay engaged, which makes it harder to force back with a knife, card, or shove.

Deadbolts improve security by anchoring the door slab to the jamb with a thicker, longer-throw bolt. The lock only works well when the strike plate, screws, and surrounding frame are strong enough to resist splitting under force.

Types

Single-cylinder deadbolts use a key outside and a thumb-turn inside. Double-cylinder deadbolts use a key on both sides and are sometimes installed near glass, though local code can restrict them because they slow emergency egress. Smart deadbolts add a motor, keypad, or app control but still depend on proper door alignment.

Where It Is Used

Deadbolts are used on front doors, back doors, garage entry doors, and some side doors. They are also common on rental units, accessory dwelling units, and detached structures where improved forced-entry resistance matters.

How to Identify One

A deadbolt is usually mounted above the door knob or lever. From the edge of the door, the bolt is a solid rectangular or cylindrical piece that throws into a reinforced strike plate when locked.

Replacement

Replacement is common when the lock binds, the key stops turning smoothly, the bolt will not extend fully, or the hardware is loose after years of use. If the door or frame is out of alignment, replacing the lock alone may not solve the problem.

Deadbolt — FAQ

What is the difference between a deadbolt and a regular door lock?

A regular knob or lever lock usually has a spring latch that can be easier to force back. A deadbolt uses a solid bolt that throws deeper into the frame and provides better resistance to forced entry.

How do I know if my deadbolt needs replacing?

Common signs include sticking keys, a bolt that will not throw fully, loose hardware, or a lock that only works when you push or pull the door. Those symptoms often point to wear, poor alignment, or both.

Can I replace a deadbolt myself?

Many homeowners can replace a deadbolt if the door prep matches the new lockset. The more important issue is making sure the strike plate is secure and the bolt lines up cleanly with the frame.

Do smart deadbolts work as well as standard deadbolts?

They can, as long as the hardware is well made and installed on a properly aligned door. The convenience features do not matter if the strike plate, screws, or jamb are weak.