The lock will not turn

What has probably happened

• Wear inside the cylinder after years of use.
• Dirt, grit and old grease packed into the mechanism.
• The door has dropped or swollen, so the bolt is binding in the frame rather than the lock being at fault.
• Corrosion, especially on coastal or exposed doors.
• A worn key that no longer matches its own lock.
• Frozen mechanism in cold weather.

What the technician does

• Working out whether it is the lock or the door — very often the alignment is the problem and the lock is fine.
• The cylinder serviced and correctly lubricated.
• Hinges, strike plate and alignment adjusted where the door has moved.
• Cylinder or lockset replaced where it is genuinely worn out.
• A fresh key cut where the key is the worn part.

Questions people ask

Is it the lock or the door?

Often the door. If the bolt only binds when the door is closed but turns freely when open, the door or frame has moved and the lock is fine — an adjustment fixes it.

What should I use to lubricate it?

A lubricant made for locks. Household oil and general-purpose sprays gum up with dust over time and leave you worse off than before.

It only sticks in cold weather.

Moisture inside the mechanism freezing. It usually points at a worn or exposed cylinder, and a service or replacement sorts it.