Remove these screws unscrew one side of the door knob and pull the door handle and lock assembly out of the door.
Home front door lock wont unlock at all.
You can spray a little dry lubricant in the lock to free up the plug so you can open the door.
Lubricate the moving components with graphite then replace any broken parts and reassemble the lock.
Outdoor locks can collect a lot of dirt and dust inside the lock cylinder.
Spray the door key with a graphite based lubricant.
That can cause the pins to get stuck in a partially raised position and prevent the plug from turning.
The lock cylinder may be broken so that you cannot use your key or anything else to move your door lock into the unlocked position.
The same solutions apply to when you are solving the issue with most broken locks.
This video shows how to disassemble and lubricate a basic cylindrical doorknob.
A strike plate is usually affixed to the door jamb and facilitates the extension of the bolt or latch.
Remove the old lock.
Flip the key and open the door.
The door could be misaligned so that although the door can be unlocked while the door is ajar when closed the door cannot unlock.
If that is the problem it is easy to fix.
In most cases it means that the latch or locking bolt are not lining up with the door locks strike plate.
Misaligned deadbolts and latches are common door lock problems.
If the malfunctioning lock is in the door handle there will be at least two screws securing the door handle to the door.
If the key turns but doesn t unlock the lock disassemble the lock so that you can be sure the cam or tang is properly engaged with the bolt.