An internal mortice lock is a key operated lock which can be fitted to internal doors, such as your bedroom, study, or closet door, for additional security. To ensure that your DIY installation runs smoothly, we are sharing our top tips for fitting a mortice lock to an internal door.

Before ordering a mortice lock, measure the width of the door stile and the thickness of the door. These measurements will enable you to identify the size of the lock body that is required. The two standard sizes include a 63mm width with a 45mm backset, and a 76mm width with a 57mm backset.

Once you have cut the mortice and the faceplate recess, hold the lock body against the face of the door and mark the position of the keyhole.

It’s easy to weaken the door if you drill too deeply into the door stile. To avoid any damages, wrap some tape round your drill bit so you can see when you have drilled holes to the required depth. Some drills feature a depth stop attachment which is handy for this task.

Do not blow into the mortice to clear out the shavings. Doing so may leave you with an eye full of splinters and dust, instead remove the wood shavings with the drill bit, a narrow chisel or vacuum.

Creating a wider mortice than required will weaken the door so much that is could split around the lock if forced. Avoid this type of damage by choosing a drill bit that is only slightly wider than the thickness of the lock body.

Before testing the fit of the mortice lock, make sure to turn the key to extend the bolt of the lock. If it gets stuck, you can then grip the bolt with pliers and pull the lock body out again.

With the lock fitted, measure the distance between the bolt and the closing face of the door. Use this measurement to position the keep plate on the door frame so that the bolt just engages in the recess when the door is locked.

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