How do Mortice Locks Work?

A mortice lock relies on a relatively large mechanism, which slots into the interior of the door. This means that the door in question must be of a certain thickness, in order to accommodate the lock. Inside this mechanism is a space for the bolt to retreat into, as well as a series of parallel levers which are attached to the rear of the bolt via a small piece of metal called a bolt-stop. The cut of the key is designed to match the levers on the interior of the matching lock. If the right key is used, then all of the levers align, and the whole mechanism can be rotated to withdraw and extend the bolt. If the wrong key is used, the key either won’t fit into the lock, or it won’t catch all of the levers in the right way. A mortice lock will also incorporate several other components. These include the strike plate, and a piece of metal surrounding the mortice. This ensures that the bolt slots straight in, rather than scuffing against the surrounding wood. There’s also the faceplate, which is often a separate piece of metal that attaches to the door, facing the strike plate. Finally, the escutcheon plates sit around the handle to preserve the look of the door. It serves no function beyond aesthetics.

What Type of Doors are Mortice Locks For?

Mortice locks are primarily found on external doors. They can, however, also be used on internal doors to control who has access to certain parts of the house. You might do this if, for example, you’re running a bed-and-breakfast, or you’d like to keep garage doors under lock and key for security reasons.

What’s the Difference Between a Mortice Deadlock and a Mortice Sashlock?

Mortice locks come in a few different varieties, the most common being deadlocks and sashlocks. Deadlocks are the simplest. They only have a keyhole, and a bolt that goes back and forth. Sashlocks, on the other hand, feature a handle-operated latch mechanism. This means you can open and close the door without having to use the key, but can still lock the door when you leave the building.

Are Mortice Locks Secure?

Mortice locks are popular for a good reason - they offer excellent security and reliability. But some mortice locks are more secure than others. The more levers there are inside the mechanism, the more difficult the lock will be to pick. Those with five levers or more are generally considered to be the standard mortice lock for external doors – though three-lever locks are cheaper to produce and buy, making them a good choice for internal doors. You can also buy seven-lever mortice locks, which are somewhat more secure than five-lever mortice locks. The main thing to look for is a mortice lock that’s compliant with the BS3621 standard or above. This basically certifies that the lock is sturdy enough that it can’t be dismantled from the outside. Specifically, it should last for five minutes when a tester tries to drill or cut through the bolt, and the bolt will need to extend two centimetres into the mortice. Another thing to look for is the British Standard kitemark, which is the industry’s mark of quality. The Metropolitan Police recommend combining a mortice deadlock with a double-locking nightlatch, so you have some redundancy when it comes to security. That way, if one device fails, you’ll have another to fall back on. Other police services offer similar advice. Rear and patio doors are often targeted by thieves, as the intruder doesn’t have to try and gain entry in view of the street. These sorts of doors are generally supplied as a single unit that can’t be modified with additional locks. Modern patio doors are far more substantial than those of yesteryear, so if this is a concern, you might want to upgrade your French, sliding, or bi-fold doors.

So, Should You Buy a Mortice Lock?

A mortice lock is a standard across the country, thanks to a robust and resilient design that’s stood the test of time. While the internal mechanisms will be of interest to engineers, most of us only think about our mortice locks when they stop working. Invest in one that’s of the required standard, however, and this is unlikely to happen!

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Technical Tips

What is a Door Jamb?

What is a Mortice Lock?

How to Replace a Door Jamb

Storing Internal Doors

Guide to Trimming Hollow Core Doors

Different Door Styles, Finishes and Compositions Explained

Bi-Folding Doors and Traffic Doors

Questions to Ask Before Buying a New Door

Installing a Peephole in a Wooden Door

How to Properly Measure for a New Door

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