Buying Guide · Locks and Latches

Mortice Lock or Tubular Latch? How to Tell What You Have and What to Replace It With

Look at the edge of your door. A small plate about 25 mm wide with only a latch tongue means a tubular latch. A tall plate, usually 175 mm or more, with a latch and often a deadbolt means a mortice lock. Replace like-for-like whenever you can, because the hole already cut in the door decides what will fit.

Getting this wrong is the most common reason door hardware is returned. A mortice lock will not go into a tubular-latch door without extra cutting, and a tubular latch leaves a large empty pocket in a mortice-lock door. This guide shows you how to tell which one you have, what to measure, and which replacements drop straight in.

The 30-second test

Open the door and check these four things. Two or more pointing the same way gives you your answer.

1. Faceplate on the door edge. Tubular latch: short, about 57 mm tall and 25 mm wide, held by two screws. Mortice lock: tall and narrow, usually 175 to 240 mm, with screws at the top and bottom.
2. What comes out of the edge. Tubular latch: one sloped latch tongue only. Mortice lock: a latch tongue, and often a square deadbolt and a small trigger (auxiliary deadlatch) beside it.
3. Keyhole position on the door face. Tubular latch: no keyhole, or a key in the centre of the knob or lever. Mortice lock: a separate keyhole (oval or Euro cylinder) above or below the lever.
4. Door furniture. Tubular latch: usually a round or square rose behind each lever. Mortice lock: often a long backplate covering the lever and keyhole, though roses with a separate escutcheon are also common.

Still unsure? Take the lever off (usually one grub screw underneath) and remove the two faceplate screws. A tubular latch slides out as a small cylinder. A mortice lock is a flat rectangular box that won't come out until both levers and the cylinder are removed.

Tubular latches: the everyday interior option

A tubular latch is a small metal tube fitted into a round hole drilled in the door edge. The lever or knob on each side turns a square spindle that runs through the latch and pulls the tongue back. Almost every internal door in an Australian home built in the last 30 years uses one.

Where you'll find them: bedrooms, bathrooms, laundries, linen cupboards and hallway doors, paired with privacy levers (a snib inside, emergency release outside) or passage levers (no lock).

The measurements that matter:

• Backset: door edge to the centre of the lever. 60 mm is standard on Australian doors; 70 mm is common on older homes and wider stiles. Some latches adjust between the two.
• Edge bore: the round hole in the door edge, typically 25 mm in diameter.
• Faceplate: about 57 to 60 mm tall and 25 mm wide, with square or round corners. Match the corner shape or the old rebate will show.
• Spindle: most lever sets use an 8 mm square spindle. Check this if you're pairing a latch from one brand with levers from another.

What a tubular latch can't do: it has no deadbolt and no separate keyed cylinder. For a lockable front or back door you need a deadbolt alongside it, or a mortice lock instead.

Mortice locks: for entry doors and heavier duty

A mortice lock is a flat rectangular lock body that sits inside a deep slot (the mortice) cut into the door edge. It holds the latch, the lever hub and a keyed cylinder in one case, and usually a deadbolt as well.

Where you'll find them: front and back entry doors, commercial and fire-rated doors, apartment entries, and narrow-stile aluminium shopfront or sliding doors.

The measurements that matter:

• Backset: door edge to the centre of the lever. 60 mm is the most common size on timber entry doors; narrow aluminium doors use short backsets such as 28, 30 or 35 mm.
• Centres (pitch): the distance from the lever spindle to the cylinder. This decides which backplate fits, so measure it before choosing furniture. 85 mm is common on Euro-style locks.
• Lock body size: height, depth and thickness of the case. A dormakaba MS2600, for example, needs a 120 × 90 × 20 mm opening.
• Faceplate: length and width, and whether the corners are square or rounded. Usually 175 to 240 mm long and 22 to 25 mm wide.
• Cylinder type: oval (common on Australian residential locks) or Euro profile. The replacement must take the same type.
• Function: entrance, storeroom, classroom, privacy and so on. The model code stamped on the faceplate (for example dormakaba MS2602) lets a supplier find an exact match.

Side by side

	Tubular latch	Mortice lock
Hole in the door	Round 25 mm bore in the edge	Deep rectangular slot in the edge
Faceplate size	About 57–60 × 25 mm	About 175–240 × 22–25 mm
Common backsets	60 mm or 70 mm	60 mm on timber doors; 28–50 mm on aluminium
Deadbolt	No	Usually yes
Keyed cylinder	No (or in the knob)	Yes, separate oval or Euro cylinder
Typical doors	Internal: bedrooms, bathrooms, cupboards	Entry, commercial, fire-rated, aluminium
Install difficulty	Easy DIY with a drill and spade bit	Mortising jig or a locksmith if cutting new
Typical lever furniture	Lever on rose	Lever on backplate, or rose with escutcheon

What to measure before you buy

Take these with the old lock still in the door, then again with it out. Bring the old latch or lock to the showroom if you can.

1. Backset: from the door edge to the centre of the spindle hole. Say 60 or 70 mm, not "about 2 inches".
2. Faceplate: height and width, and whether the corners are square or round.
3. Door thickness: standard internal doors are 35 mm and entry doors 40 mm or more. Most latches and locks list the range they suit.
4. Mortice locks only, centres: spindle hole to cylinder hole, centre to centre.
5. Mortice locks only, lock body: height, depth and thickness of the case once it's out.
6. Mortice locks only, cylinder: oval or Euro profile, and its length if it's a Euro cylinder.
7. Model code: any brand name or number stamped on the faceplate or case. Photograph it.
8. Photos: the door edge, both faces of the door, and the old lock out of the door.

What to replace it with

Match the type, backset and faceplate of what's already in the door, and only change type when the door's job has changed.

What you have	What you want	What to buy
Tubular latch on an internal door	New levers, same function	Any lever set with the same backset; reuse the latch if it still works
Tubular latch on an internal door	A lockable bathroom or bedroom	Privacy lever set or a separate privacy turn; no new holes needed
Tubular latch on an external door	Better security	Keep the latch and add a deadbolt, or have the door mortised for an entrance mortice lock
Mortice lock on an entry door	Same lock worn out	Same brand and model (check the faceplate code); the lock body and cylinder drop straight in
Mortice lock on an entry door	New look	New lever furniture with the same centres; keep the lock body
Mortice lock on an internal door	Simpler hardware	A mortice latch or privacy mortice lock with the same body size, so the slot stays covered
Aluminium sliding or bifold door	Replace the lock	A narrow-case or hook-bolt mortice lock with the same short backset

Switching from mortice to tubular leaves a large slot behind a small faceplate. It needs a timber fill and repaint, so it's rarely worth it.

Switching from tubular to mortice means cutting a deep slot in the door edge. A hollow-core internal door may not have enough solid timber, so check before you buy.

Frequently Asked Questions