Open the door and look for a telltale kiss on the strike plate.
Front door deadbolt not lining up.
Loose door locks door knobs and door handles.
Reinstall the plate and test the dead bolt.
One possible reason for this is that your door isn t properly aligned.
Unscrew the strike plate from the door jamb clamp it in a vise then file it down to the chalk mark above right.
A strike plate is usually affixed to the door jamb and facilitates the extension of the bolt or latch.
To line up the lock and the strike plate so that the lock goes into the hole easily try filing around the edge of the actual lock and the strike plate.
If the door is sagging and will not line up with the latch check the door hinges.
File only the sides that are needed in order to have a proper fit for the lock.
Luckily fixing the alignment of your door doesn t have to be a chore.
For instance some of the best front door locks are a mixture of mortise locks.
Lift the door up to relieve the pressure on the hinges and tighten the screws.
If it s still not locking file away a little more of the strike plate until the bolt locks properly.
In that case take the hinges from the frame.
If the screws have been stripped they will not tighten in the holes and you ll need new ones.