How to fit a Yale lock

Video by Tommy's Trade Secrets. This walk-through is based on the video "Tommy's Trade Secrets - How To Fit A Yale Lock" from Tommy's Trade Secrets, a long-running UK trade DIY channel with clear, practical demonstrations. The section on positioning the case at the right height and marking the cylinder hole through the door is particularly useful if you are replacing an old lock rather than fitting from scratch.

1. Choose the right lock and check your door thickness

Yale-style nightlatches come in a few different backset sizes — the distance from the door edge to the centre of the cylinder. The standard backset for most UK front doors is 40 mm, though some older doors use 44 mm. Check before you buy; it is a small thing that catches people out. The lock body will usually state the backset on the packaging.

Also check your door thickness. Most timber front doors in East Kent homes are between 40 mm and 45 mm thick. If you have a solid hardwood door on the thicker side, buy a cylinder with a longer barrel. Most Yale lock kits include an adjustable cylinder that covers the common range, but it is worth double-checking. A cylinder that does not reach flush with the door face is a security weakness.

2. Mark the lock case position on the door edge

The standard fitting height for a Yale nightlatch is roughly 1 m from the floor, measured to the centre of the case — though on older UK doors you are often matching an existing mortice or fitting around a letterbox, so use your judgement. Hold the lock case against the door edge, centred at your chosen height, and mark around it in pencil.

Most Yale cases sit flush with the door edge and screw directly into it. Mark the screw hole positions carefully. If the door edge already has a shallow recess from a previous lock, clean it out rather than trying to fill it — the new case will often sit quite naturally in an existing recess as long as the dimensions are similar.

3. Drill the cylinder hole through the door face

This is the step that makes people nervous, and fairly so — you are drilling a 32 mm hole clean through a door you would rather not ruin. Use a hole saw rather than a spade bit; it leaves a cleaner edge. Mark the centre of the hole on both faces of the door before you start. Drill from one face until the pilot bit just breaks through the other side, then finish from that side. This avoids the splintering you get when the hole saw exits a timber face at speed.

The centre of the cylinder hole should align with the horizontal centreline of the lock case. Most Yale kits include a paper template — use it. Tape it to the door face, double-check the alignment, and only then pick up the drill.

4. Fix the lock case and fit the cylinder

Screw the lock case to the door edge using the screws provided. Keep it square — a case that is slightly twisted will cause the latch to bind. Tighten the screws firmly but do not strip them; they are going into timber end-grain, which is not as strong as face grain.

Feed the cylinder through the hole from the outside, then connect the connecting bar to the back of the lock case on the inside. The connecting bar drives the latch mechanism when you turn the key, so it needs to engage properly. Secure the inside plate with the two machine screws that pass through the door and into the cylinder. Do not overtighten — the cylinder should sit flush and feel solid, not crushed into the door.

5. Mark and fit the keep on the door frame

Close the door to its natural position and apply a small amount of chalk or pencil lead to the face of the latch. Push the door firmly shut and open it — the chalk will leave a mark on the door frame exactly where the latch strikes. That is your keep position.

Hold the keep box over the mark and draw around it. Chisel a shallow recess so the keep sits flush with the frame face. This is worth doing neatly; a proud keep will stop the door from closing fully. Drill or chisel the latch pocket behind the face plate, fit the keep box, and screw it down. Test the door from both sides before declaring it done.

6. Test and adjust the latch and deadlock

Most Yale nightlatches have two functions: the spring latch, which snaps shut when you pull the door to, and a deadlock that engages when you turn the key fully. Test both. The latch should click home cleanly with no resistance; if it is binding, the keep needs to move very slightly up, down, or sideways. Most keeps have slotted screw holes for exactly this purpose — slacken the screws, nudge the keep, retighten.

Check the snib on the inside — that is the small lever that holds the latch back so you can exit without a key. It is a common source of locked-out situations if it gets knocked accidentally, so make sure the household understands how it works. That said, Yale nightlatches are fairly forgiving once everything is aligned, and most adjustments take five minutes rather than a full rehang.

When to call a handyman

Call Richard if the door frame is soft or damaged and will not hold the keep screws, if the door itself has swollen or dropped and needs planing before the lock will sit correctly, or if you want a second lock added at the same time for better security. Older front doors in Sandwich often have a mix of lock types that do not quite align with modern fittings — sometimes a fresh eye and a few extra fixings makes the difference between a lock that works properly and one that technically closes but would not stop anyone determined.