A deadbolt is a locking bolt that throws into the door frame on its own. It works independent of the door’s latch. That adds security beyond a standard lockset. A single-cylinder deadbolt takes a key outside and a thumbturn inside. A double-cylinder deadbolt takes a key on both sides.
Are double-cylinder deadbolts safe?
A double-cylinder deadbolt can trap people during an emergency. Someone inside needs a key to unlock it and get out. If no key sits within reach, the door holds them in. On many commercial and public buildings, code restricts this setup on exit doors. Check local code before you install one.
Why does a deadbolt key turn loosely?
A loose set screw is one of the most common cylinder problems. That screw holds the cylinder in place. Watch for a keyway that sits off vertical or spins freely. Both point to the same loose screw.
The fix is straightforward in most cases. A technician squares the cylinder so it engages the lock. Then they tighten the set screw back down. A tailpiece on the cylinder’s back drives the bolt. In extreme cases that tailpiece bends or breaks and needs replacement.