Unless you fit a bs 3621 night latch will require an additional lock fitted to your door to improve security such as a mortice lock.
How to fit a mortice lock to an external door.
Fit the lock back in the door so that the front plate is flush with the edge check the positions of the holes for the key hole and door handle spindle from both sides of the door if necessary remove the lock and adjust the size and or position of the holes so that they line up with the appropriate parts of the mortice lock body.
The minimum door width is 45mm or 1 75 inches.
Then mark and drill screw holes to fix it in place.
A mortise lock in a very strong special locking system fitted to the inside of a door.
To prepare the mortice slot for the lock start by marking the centre of the thickness of the door.
Difference between rim locks and mortice locks the difference between a rim lock and a mortice lock is that a rim lock is fitted on the surface of the door whilst a mortice lock is fitted in the door edge.
Fit the lock and check the positions of the door handle spindle and key hole adjust these if necessary.
Fit the lock into the door and secure using screws.
Chisel a recess for the faceplate.
Here are six things you need to know about mortise locks for residential door security.
Chisel away a small amount of wood at a time to open the drill holes into a clean rectangular hole to fit your lock.
Using a sharp chisel cut out the rectangular recess on the edge of the door to take the front plate of the lock.
This will be your guide when drilling.
When the mortice lock space is chiselled out insert the lock and outline the faceplate with a marking knife.
As a guide the height of your lock should be about 1 metre high step 2 using your measurement mark out both the top and bottom of the latch step 3 measure and mark out a vertical central line.
Step 1 measure where the lock will fit on the door.