There are two basic types of lock for the main doors of a house:
A simple night latch lock does not provide adequate security on its own. They are too easily forced to provide adequate security on their own.
A better option is the deadlock type cylinder rim lock. These are designed to lock as the door is closed but can also be double-locked with the key. This means that the lock cannot be operated by turning the knob on the inside which will prevent easy exit should an intruder break-in elsewhere.
Marking out for the lock
The lock will be supplied with detailed measurements for fitting, usually in the form of a template. This is held against the door in the required position and the various fixings are marked.
The lock has a protruding edge which should be recessed into the door. Mark this recess using the template or by holding the lock against the door.
Drilling and cutting
Use a sharp chisel to cut the outline and pare out the waste. Check the lock fits neatly in the recess and its lip sits flush with the door edge.
Mark the centre of the hole for the cylinder itself and bore this out using a drill bit of the specified diameter. Drill from the inside to a point where the bit just begins to emerge through the face of the door. Stop drilling and work from the outside thus preventing the exterior wood from splitting.
Be careful to hold the drill at right angles and level so that the hole runs true.
Insert the cylinder through its mounting plate ( like a large washer ) and into the door. Depending on the thickness of the door, you may need to trim the bar which operates the locking mechanism. Check how far this bar needs to sit into the lock, and trim accordingly. Hold the bar in a vice on your workbench and cut with a hacksaw. Once trimmed, use a file to clean off the burr to ensure easy fitting and smooth operation.
Fitting the lock
Fasten the backplate to the door and fix the cylinder using the screws provided. Mount the lock itself onto the backplate and secure this with screws provided.
Hold the strike plate over the latch, close the door as far as the frame edge and draw round it with a pencil line. To ensure that there will not be too much ‘free play’ in the door, the strike plate must be positioned to hold the door firmly against the doorstop. See door latch strike plate fitting. The plate must be recessed into the frame as specified to provide adequate security. Notch out the recess using a sharp chisel. Fix loosely with one screw, and check alignment before fitting the remaining screws and tightening.
Mortice lock with or without latch
This type has the lock recessed into the door edge.
They are available in different sizes enabling the handle itself to be located either closer to, or further from, the door edge.
Marking out for the lock
Mark the centre line of the lock edge of the door. Hold the lock flat against the door edge and mark the top and bottom. Now measure the thickness of the lock and mark this symmetrically about the centre line. You should now have a rectangle marked on the surface ready for cutting.
Drilling and cutting
Using a drill a little thicker than the lock itself, drill a series of holes within this outline to the appropriate depth into the door. If you do not have a depth gauge on your drill, simply mark the required depth on the drill bit with chalk.
Now cut around the outline with a sharp chisel and pare out the waste. Do this in stages, each time cutting along the outline first to keep the edges clean. Be careful not to cut too deep at each stage, as the sides will split if the chisel is forced too far into the wood. Use the flat side of the drill against the outside edges of the recess. Using the chamferred side against the edge will cause the chisel to drift off course.
Slide the lock into the recess and mark the perimeter of the face plate. Using a sharp chisel, cut along this outline to a depth equal to that of the plate. Make small cuts across the grain within the outline and pare out the waste with the chisel. Hold the lock back to front and offer only the plate into the recess. If you insert the whole lock at this point, you may find it difficult to remove. Sit the plate into the recess to check that it fits flush with the surface.
Mark the position of the fixing screws and drill pilot holes for them. If the back of the plate is shaped for the screw fixings, use a countersink tool to bore out a recess for these. Hold the lock against the face of the door so that the plate is flush with the door edge. Mark through the keyhole of the lock on the horizontal line previously drawn on the door face.
Using a drill bit a little larger than the keyhole, drill a set of holes through the door to produce the opening at this mark. Take care as you reach the far side, as excessive pressure on the drill will cause the other face to split. Keep the drill square and level or the key will not easily fit into the lock.
Use a padsaw to trim these drill holes into a slot to accommodate the key.
Clear out all the debris from the work using the crevice tool on a vacuum cleaner.
Fitting the lock
Push the lock into its housing and ensure that it lines up with the keyhole before fixing in place with the screws.
Position the key hole covers on both faces and check the operation of the key in the lock.
Lock and latch
With the lock and latch type, a hole must also be drilled for the spindle before inserting the lock and the handles fitted as for a mortice latch
Marking out the strike plate
With the new lock fitted, close the door against the frame so that the lock bolt (and the latch) touch it.
Mark the top and bottom of these on the frame and open the door again.
Transfer these lines horizontally on the frame rebate.
As with a simple mortice latch, measure the distance from the closing edge of the door to the far edge of the latch.
Mark this distance from the doorstop on the frame rebate.
Hold the strike plate in position on the frame so that the far edge of the cut out lines up with the mark just made and the horizontal lines match up with the top and bottom of the cutout.
Recessing and fitting the strike plate
Mark around the strike plate and recess the frame to suit.
Check that it fits flush in the recess before drilling pilot holes for the screws, and fixing in place. If necessary, counterbore the pilot holes to accommodate the screw housings on the back of the plate.
Check the operation of the lock when the door closes to ensure all items are lined up properly.
Slight adjustment in any direction may be made by slackening the strike plate screws and moving the plate. Holding it firmly in its revised position, re-fasten the screws.