You can tighten a simple interior mortise lockset like the one shown at left as follows.
How to fix my front door lock.
3 if this does not help remove the knob.
Using gloves dry the key and insert it slowly into the lock.
Shut the door and try to lock it.
The basics of how to fix a door lock that is jammed in this way comes down to heat.
Don t call the locksmith just yet.
2 hold the knob on the other side of the door and turn the loose knob clockwise until it fits snugly.
If it won t lock open the door.
Equip a rotary tool with a carbide tip bit.
You can heat your key or use a blow dryer to thaw the door lock.
1 loosen the setscrew on the knob s shank.
If it is loose or has slipped out of the mortise place it back in the mortise and tighten the screws with a phillips screwdriver.
If the weather is very cold don t discount the possibility that the lock might have frozen.
Inspect the strike plate on the edge of the door frame.
The best way to thaw out a lock is to insert a heated key into it.
Warm the key by placing it on top of a radiator or in a bowl of hot water.
In some cases you will have to use a de icer on your locks to resolve the problem.