6 Things You Need to Know About Mortise Locks for Residential Doors

Mortise lock

By Xaaxll (Own work) [CC BY-SA 3.0], via Wikimedia Commons

There are lots of things we can do to improve doors security, and upgrading the locks is one of the top priorities. Door security is important because it’s the preferred point of entry for most burglars. Even though glass windows are more fragile compared to solid doors, a housebreaker will always try the doors first. This includes all doors, not just the front, so that means side doors, back doors and especially patio doors. In this piece we focus on the benefits of using mortise locks. Any door is only as strong as its lock. One that is weak, easy to pick or remove makes you vulnerable.

Here are six things you need to know about mortise locks for residential door security.

#1 – The Mortise Lock Defined

A mortise lock in a very strong, special locking system fitted to the inside of a door. To use a mortise lock your door must be thick enough to accommodate it. The minimum door width is 45mm or 1.75 inches. If you want to improve your door security, just know that this type of lock offers far better protection against intruders than the common cylinder locks.[1]

#2 – Reasons to use a Mortise Lock?

Here are four basic reasons why you want to use a mortise lock over other lock types:

  1. Burglars prefer to break in through doors, so improved door security is paramount
  2. Mortise locks are reliable and strong, thus offering good door security [2]
  3. The classical appearance makes them more attractive than cylinder locks
  4. They’re versatile, so you can use them with all kinds of door furniture and cylinders

#3 – How Mortise Locks Work?

The mortise lock has to fit neatly into the mortise cut-out, or pocket, made in the door. There are four essential parts to the lock:

  1. The mortise lock (latent once installed)
  2. The lock trim (door lever, door knob or door handle)
  3. The strike plate (metal lining for the hole within the door frame)
  4. The keyed cylinder (it’s where the lock and unlock function occurs)

The housing for the bolt is the ‘lock body’. This is where the mechanical components are that engage and disengage the actual lock. These components include:

  • Mortise cylinder
  • Deadbolt (bolt only), or…
  • Sashlocks (a door catch plus a locking bolt)
  • Auxiliary latch
  • Latch bolt
  • Lever trim

The door handles or door knobs turn to withdraw the latch once the door’s unlocked. There’s also the ‘through-spindle’.  This is simply the long rod that links the door handle or knob to the mortise lock body. A threaded ‘lock cylinder’ lets you unlock the door once you insert the key. The ‘cam’ component is a rectangular piece of metal that rotates to retract the door latch. The size and weight of a mortise lock means they can withstand considerable usage. Note that because there’s quite a bit going on inside a mortise lock, they do need simple servicing periodically.

#4 – Doors Best Suited to Mortise Locks

Almost all burglars and intruders will try to enter a residence from the front door of a property. Needless to say, this is your priority door when it comes to home security. All the same, if you have other entrance doors, you might want to consider using the locks on those too. Not all burglars give up if they can’t break in via the front door, which is why all entrance door security is important.

#5 – When to Use a Mortise Lock

You should consider using a mortise lock on any door that isn’t kick-proof or pick-proof. If you’re not sure, ask a security expert to assess your door security. Door frames are important too. It’s no good having a quality, solid door with a strong lock on a weak frame.

#6 – Ideal Candidates for Mortise Locks

Obviously there are people who live in areas with high crime rates and those who live in low-crime neighborhoods. But it’s important never to become complacent when it comes to good home security. Don’t be fooled into thinking you’re 100% safe in an apartment building either, especially if it’s a large complex. Burglars can and do find their way into these places, looking for easy access via weak entrance doors. Therefore, anyone who has doors that are not as secure as they could be, is an ideal candidate for mortise locks and other door security.

Fitting a Mortise Lock

Before ending this piece, I just want to give a word of caution about fitting mortise locks to your doors. If you’re a Handy Andy around the home, then you shouldn’t have any problems. If you’re not, then it’s perhaps better to get someone who knows what they’re doing. Compared to a cylindrical type lock, the mortise lock is a lot more difficult to install. Remember, there has to be a precision cut into the actual door to house the lock. You also need to fit the trim to the mortise, which is not advisable unless you’re a handyman. Precision is crucial here, and anything less will end up in a botch job that looks awful and malfunctions. In fact, a poor fit is something that could even ruin an otherwise good door, so please take heed.

Before You Decide

The two considerations before you make a decision are the installation and type of mortise lock. Please, please, please get a professional to fit it if you’re not up to the job. For the lock itself you can choose from sashlocks and deadlocks. The sashlocks come with both a door catch and a locking bolt. Deadlocks only feature a single bolt. Most people prefer sashlocks for home doors as they have a door spindle. This spindle allows you to easily open the door from the inside without needing a key.


  1. http://www.doityourself.com/stry/what-is-a-mortise-lock
  2. https://www.safety.com/blog/7-tips-for-burglar-proofing-doors/

About Mark Bickmore

Hi, my name is Mark Bickmore. I'm an Engineer, who has a keen interest in home security and keeping my family, property and valuables safe from burglars. This website was set up to help me explore the research, facts and myths about burglars and burglary. Please feel free to contact me should you have any questions, comments or suggestions.

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