Seized & Jammed Lock Opening: preparing for the visit

The old mortise lock on the front door of the house turns the key halfway and stops with a dull clunk. It has been getting harder for months, and the brass key is starting to show a bend.

Worth answering before the call

Is the key worn, bent, or a copy made from another copy? Is anyone inside, and can the door be opened from that side? Do you have identification, a lease or a management contact for the property?

How do I stop this from happening again?

Three habits cover most of it. Lubricate the cylinder with a dry lock product twice a year and keep oils out of it. Check that the door locks with no pressure on it each spring and fall, snugging hinge and strike screws when it starts to drag. Keep a lock de-icer handy and fit a keyhole cover on exposed doors. And act on the first stiff turn, because a lock that still turns is a smaller job than one that has stopped.

Will I need a whole new lock?

Usually not. Most jammed locks are saved by cleaning the cylinder, fitting a small part such as a tailpiece or spring, or adjusting the door so the bolt has room. A new cylinder is fitted when the plug or shell is corroded through or twisted by forcing, matched to your finish and, where possible, pinned to your current key. A complete new lockset is usually a choice you make rather than a requirement, though some internal failures cannot be serviced in place and call for a full replacement.