How do I fit a night latch to a front door?

Getting the height and backset right, cutting the connecting bar to the door thickness, and the difference between a plain latch and one an insurer will accept.

Difficulty: intermediate
Time: 1 hr 15 min
Read: 5 min
Safety: caution

Short answer

Mark the height and backset from the template, drill the cylinder hole from both faces, cut the connecting bar so it enters the case by the right amount, screw the backplate to the door, hook the case on, then fit the staple on the frame so the latch enters squarely. Buy an automatic deadlocking version.

A night latch — a rim latch, and universally called a Yale after the best-known make — is the lock on the inside face of a traditional front door. It holds and latches the door on its own, which is why it usually pairs with a mortice deadlock rather than a sashlock. Fitting one is mostly drilling one hole accurately and cutting a bar to length.

Safety

A night latch is often the only thing holding a front door shut. Fit it into solid timber — the door stile and the frame itself — and never into a thin lining or a decorative moulding. A staple screwed into 8mm of architrave will come off in one shoulder charge and gives an entirely false sense of security.

What you'll need

The night latch, with cylinder, connecting bar, backplate, case and staple
A hole saw or flat bit to the size on the template
A hacksaw or the score-and-snap line on the bar
A sharp chisel
A drill and screwdrivers
The paper template from the box

The parts of a rim nightlatch and how they sit on the door

Step by step

Check what the door is made of.The latch fixes into the lock stile — the vertical solid member on the closing edge. On a hollow-core door there is only a narrow lock block and a night latch usually cannot be fitted safely. On a panelled door make sure the position clears the panel groove.
Set the height.Conventionally around shoulder height, well above a mortice deadlock, and clear of any rail joint. Above the mid rail on a panelled door is the traditional position and it is traditional because that is where the timber is solid.
Use the template for the backset.The paper template in the box gives the distance from the door edge to the centre of the cylinder hole for that particular latch. Fold it round the edge of the door so the same marks appear on both faces — that is the whole point of it.
Drill the cylinder hole from both faces.Drill from the outside face until the pilot point breaks through, then finish from the inside. A hole saw punched straight through will tear a ring of splinters out of the inner face where the backplate may not cover it.
Drill the two fixing screw holes.From the template, again marked on both faces. These take the long machine screws that clamp the cylinder to the backplate through the door.
Cut the connecting bar to length.The flat bar out of the back of the cylinder must enter the lock case by the amount the instructions specify — typically a few millimetres past the mechanism. Most bars have score lines; snap or saw at the right one, having measured against your actual door thickness plus the backplate.
Fit the cylinder and backplate.Cylinder through from outside, backplate on the inside, machine screws through and tightened evenly. The cylinder should sit flat and not rotate. Check the bar protrudes the right distance before going further.
Hook the case on and screw it.The case slides down onto the backplate and is held by two or three screws. Check the bar has engaged the mechanism — turning the key should now withdraw the latch.
Mark and fit the staple on the frame.Close the door and mark where the latch bolt lands. The staple must be positioned so the bolt enters squarely, with its deadlocking pin resting on the staple face rather than dropping into the aperture. Read the instructions on this — it is the step that makes automatic deadlocking work.
Chisel a recess for the staple if the design needs one.Some staples are surface-mounted, some are recessed into the frame. A recessed one must be flush or the door will not close.
Test everything, repeatedly.Door closes and latches cleanly on its own. Key withdraws the latch from outside. Inside knob withdraws it. Snib holds the latch back, and holds it locked out, if your model has both functions. Then do it twenty more times.
Consider the escape question before you finish.A night latch that can only be opened from inside with a key is a genuine hazard in a fire. Most domestic night latches open from inside on the knob without a key, which is what you want. If yours does not, think hard about whether it belongs on your only exit door.

Common mistakes

Cutting the connecting bar too short — It cannot be lengthened. Measure against your own door, and if in doubt cut at the longer score line and try it — a bar slightly too long stops the case sitting flat, which is at least visible and reversible.
Fixing the staple into architrave or a thin lining — It is the single weakest point on many front doors. Screws must reach solid frame timber, and long screws through into the structure behind are better still.
Fitting a non-deadlocking latch and relying on it — A plain latch can be pushed back with a card or through a letterplate. An automatic deadlocking model locks the bolt as the door closes, and it is what insurers expect on a night latch.

Questions people ask

Is a night latch enough on its own?

For a front door, generally not. The usual arrangement is a night latch for everyday use plus a mortice deadlock to the relevant British Standard for when the house is empty, which is also what most policies specify.

What does the snib do?

It holds the latch either permanently withdrawn, so the door does not latch, or permanently thrown so it cannot be slipped. Which functions your latch has depends on the model.

Can I fit one to a uPVC door?

No. uPVC and composite doors use multipoint locks in the door edge, and there is nothing to screw a rim case to.