Flush Bolts & Surface Bolts — Add Extra Security to Any Door
Flush bolts and surface bolts are two easy ways to add an extra layer of security to any door. Both types lock a door in place by sliding a bolt into a strike mounted in the floor or door frame — but they differ in how they're installed and where they're best used. This guide covers both.
Type 1
Flush bolts — mortised into the door
Flush bolts are mortised into wood or metal doors so they sit completely flush with the face or edge of the door. Because they don't protrude, they work on sliding doors and pocket doors with little to no clearance. They lock the door in place by sliding up into a strike mounted in the door frame above or below the door.
They're also a great childproofing solution — mount them high on the door, out of reach of small children and pets.
Top-mounted flush bolt — ideal for childproofing
Manual flush bolts
Manual flush bolts are especially useful on French-style doors — they secure the inactive leaf closed until manually unlocked by flipping a lever. On storefront doors, they allow the doors to stay open during business hours and be secured closed after hours. On double doors, they add critical security: without a flush bolt, the only thing preventing forced entry is the deadbolt.
French Door Flush Bolt
Storefront Flush Bolt
Automatic flush bolts
Automatic flush bolts are common on fire exit doors — doors that must remain closed and unlocked. Most are packaged as a set with both a top and bottom bolt.
When double doors with automatic flush bolts are closed, only the active door can open. Once the active door opens, the inactive door automatically unlocks so both can be used — ideal for auditorium and egress doors.
Type 2
Surface bolts — screwed onto the door face
Unlike flush bolts, surface bolts (also called slide bolts) are not mortised into the door — they're simply screwed onto the surface. The bolt slides into a strike that is either surface mounted on the door frame or mortised into it. Easy to install with minimal damage to the door, they can also be used on windows and gates.
Surface Mounted Strike
Mortised Strike
3 types of surface bolts
Offset Bolts
Barrel Bolts
Cane Bolts
Offset Bolts
For applications where the strike on the door frame is mounted higher than the bolt on the door.
Barrel Bolts
Can be locked in both the open and closed position — great for added control.
Cane Bolts
Longer than standard surface bolts and come with guide plates for a very sturdy application — common on double gates and heavy doors.
Security advantage
Surface bolts and flush bolts cannot be seen from the outside — so even if a deadbolt is compromised, a door with either type of bolt will still be secured. Unlike deadbolts which can be susceptible to cutting, bumping, drilling, and picking, flush and surface bolts add a layer of security that's completely hidden from any would-be intruder.
Need help choosing?
Not sure which bolt is right for your door? Contact us or call 954-776-5340. Browse our full door bolt collection or return to the Help Center.