Fix it · practical guide
The door lock that sticks: alignment before oil, key before force
In one line: A latch rubbing the strike is a door-frame problem, a dry cylinder is a lock problem, and forcing either one turns a five-minute adjustment into a trapped-key repair.
A key that works with the door open but jams when the door is closed has already told you the diagnosis: the lock is being loaded by the frame. A key that remains stiff with the door open points to the cylinder, key, dirt or internal wear. Test that difference before spraying anything into the lock or reaching for a bigger key.
The split diagnosis
- Try the key with the door open. Turn it gently in the cylinder. If it moves freely, inspect the latch and strike plate for a bright rub mark, loose screws or a door that has dropped. Tighten the hinge screws, then adjust the strike in small steps so the latch enters without being pushed sideways.
- Try a spare key. A bent or worn copy can bind even when the cylinder is sound. Keep the key straight and never twist harder because it is nearly home; a broken key in the cylinder is a locksmith job.
- Clean and lubricate correctly. Blow loose dirt away and use the lock maker's recommended dry lubricant or a small amount of suitable lock lubricant. Heavy oily sprays collect dust and can make a precision cylinder worse. Do not flood the keyway.
- Inspect the weather side. Swelling after rain, a shifted frame or paint inside the strike can change the alignment. Remove only the obstruction that is clearly rubbing; do not file away security hardware until the frame movement is understood.
The boundary between adjustment and replacement
If the lock turns with the door open but the latch will not retract, the mechanism may be worn. If the key turns but the deadbolt stops halfway, keep the door open and inspect the bolt for a misaligned strike before assuming the cylinder has failed. A lock that is loose, cracked, tampered with or protecting an exterior entry deserves a proper replacement rather than a temporary shim. The small habit that prevents a night-time lockout is to lubricate the correct way, tighten hinge screws before they loosen the geometry, and never force the key when the frame is asking for alignment.
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General information, not professional advice. Homes differ — if a job is beyond your confidence or the guide’s boundary, that is what tradespeople are for.