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HMS Locksmith is an Allston-based locksmith that repairs, rekeys and replaces door locks in homes across Boston, Brookline, Cambridge, Newton and the surrounding cities. Older houses and brownstone apartments often come with a lock that sits inside the edge of the door, a heavy brass knob and a keyhole that takes a long, simple key. Owners love the look. They are less fond of the key that will not turn in February.
Those are usually mortise locks, and the question we hear most is whether to repair them or replace them. The honest answer is that it depends on the door, the lock and what you want from it. This guide walks through how these locks work, what tends to go wrong and how to decide.
What makes a mortise lock different
A mortise lock is set into a pocket, called the mortise, cut into the edge of the door. Most modern residential locks are cylindrical locks that sit in round holes bored through the face of the door. With a mortise lock, the working parts live in a rectangular box hidden inside the door, with the knobs or levers, the keyhole and the strike plate on the outside.
Because the whole mechanism is protected inside the door, many of these locks are still doing their job long after the house was built, and This Old House calls them a hallmark of older, high-quality doors. Mortise locks have been used in American homes since the 1700s, and they remain common in commercial buildings and higher-end homes today.
Some antique mortise locks use a simple warded mechanism, with a long key often called a skeleton key. Others have been fitted with a modern keyed cylinder. That difference matters a lot when deciding what to do.
What usually goes wrong
Old mortise locks tend to fail in a few predictable ways:
- Sticking or stiff operation. Old grease hardens and dirt builds up inside the case.
- Broken springs. The spring that pulls the latch back can weaken or snap, so the knob turns but the latch does not move, or the knob droops.
- Worn parts. Levers, tumblers and the latch bolt wear after decades of use.
- The house settles, the door shifts and the bolt no longer lines up with the strike.
- Lost keys. The original key is gone and nobody made a copy.
Many of these are repairable. Cleaning, proper lubrication and replacing a broken spring can bring a sticky old lock back to smooth working order. A misaligned door often needs the strike adjusted rather than a new lock.
When repair makes sense
Our lock change and repair page sets out the basic rule: if the existing locks are in good condition and provide an appropriate level of security, they may not need replacing. For older locks that have begun to wear or corrode, or have minor damage, replacing just the cylinder is a cost-saving alternative to a complete replacement.
Repair is a good fit when:
- The lock case is intact and the problem is a spring, a worn part or dirt.
- The door is original, historic or stained, and you want to avoid visible patches.
- The lock already has a keyed cylinder that can be rekeyed or swapped.
- You live in a historic district where exterior changes are reviewed.
When replacing or upgrading makes sense
Repair is not always the right call, especially on an exterior door.
- A simple warded lock with a skeleton key is not a serious barrier on an entry door. If that is your front door lock, at minimum add a modern deadbolt or a mortise lock with a proper keyed cylinder.
- Broken or missing parts. If the case is cracked or the parts are no longer available, replacement may be the only practical option.
- Smart or keypad hardware. Many keypad and smart locks are designed for standard bored doors. Converting a mortise door to a cylindrical lock is a door-prep job, not a hardware swap. The old pocket has to be filled or covered with a plate and new holes bored.
- Fire doors. Never convert a labeled fire door yourself. The hardware is part of its rating.
A middle path is often best: keep the original mortise lock for the look on interior doors, and upgrade the security on the doors that lead outside.
Living in a historic district
If your home is in one of Boston’s historic districts, check the rules before changing anything on the outside of the house. In the Historic Beacon Hill District, all exterior work visible from a public way is subject to review by the Beacon Hill Architectural Commission. Its guidelines say original elements, including hardware, should be retained unless beyond repair, and replacement door hardware should replicate the original or be of an appropriate design. If you are not sure whether your address falls inside a district, check with the City of Boston before any visible work on doors or entries.
On Beacon Hill, for example, the Beacon Hill Architectural Commission reviews exterior work visible from a public way, which can include front door hardware.
Old doors, old houses, other repairs
A lock that suddenly binds is sometimes a symptom of something bigger. Doors swell and frames shift when there is moisture in the walls or floors, and older homes with old plumbing can hide slow leaks for a long time. If a door near a bathroom or exterior wall keeps sticking and you see staining or soft wood, the right first call may be a plumber or restoration contractor, not a locksmith.
Frequently asked questions
Can an old mortise lock be rekeyed?
If it has a modern keyed cylinder, yes. The cylinder can usually be rekeyed or replaced without touching the rest of the lock. A simple warded lock with a skeleton key works differently, so it is often better to add a deadbolt or upgrade the lock on exterior doors.
Are skeleton key locks secure?
Not very, on their own. Warded locks are generally treated as low-security, because a simple skeleton key can be made to get past the wards and open many different locks of the same type. They are fine for closets and interior doors, but an entry door needs a proper deadbolt or a mortise lock with a modern cylinder.
Trusted Local Network
We like to point readers toward businesses that do careful work in their own trades and markets. Two worth a look:
- An Orange County restoration contractor that specializes in emergency water damage drying warns that deep moisture can linger in a structure for weeks, which is exactly what makes old doors swell and bind.
- An insurance-approved company in Southern California’s San Diego, Riverside and San Bernardino counties handles water damage restoration and reconstruction, a good reminder to rule out hidden moisture when a door suddenly starts to stick.
Your Greater Boston Antique Lock Specialists
If an antique or mortise lock in your home is sticking, missing a key or no longer feels secure, reach our team through the contact page and send a photo of the lock and door edge if you can. Call (617) 249-4949 to book a visit.
HMS Locksmith is based in Allston and serves Boston and nearby communities across Suffolk, Middlesex, Norfolk and Essex counties, including Cambridge, Somerville, Brookline, Newton and Quincy. Learn more about our lock repair and replacement service, or see what neighbors say in the HMS Locksmith Google reviews before you book.
