Mortise Codes Decoded: What 6085, 4585, 3585 and 2885 Actually Mean
Open any of our push/pull lock pages and the first thing you're asked to choose is a string of four digits: 6085, 4585, 3585, 2885, or one of two "hook" versions. It looks like a model number. It isn't. It's a measurement, and it's the single most important choice on the page, because the wrong one means the lock case won't fit inside your door. This guide decodes the numbers, shows you how to measure your own door to find the right one, and explains what to do when your door doesn't match anything.
⭐ Key Takeaways
- The code reads as backset then centres: the first two digits are the backset in millimetres, the last two are the centres. So 6085 is a 60 mm backset with 85 mm centres.
- 6085 is the Australian standard on hinged doors, 4585 is the European fitting, and 3585 and 2885 are the narrow aluminium stiles.
- Two more options, 3585 hook and 2885 hook, are hook-bolt versions for sliding doors.
- Every code in the push/pull range has 85 mm centres; only the backset and the bolt type change.
- The code describes the mortise — the metal case inside the door edge — not the handle length, which is a separate choice.
- Measure the backset on your existing lock before ordering; if nothing matches, send us a photo of the door edge with a tape across it.
What a Mortise Is, and Why the Number Matters
A mortise lock isn't bolted to the surface of the door. It's a rectangular steel case that slots into a pocket cut into the edge of the door, with the handle and keypad fixed through the door from either side. That means the lock has to match the pocket: the depth from the door edge to the handle hole, and the spacing of the fixings. If the numbers are off by a few millimetres, the handle won't line up with the hole, or the case won't fit the pocket at all, and unlike a surface-mounted device there is no way to adjust around it.
Our push/pull locks are sold in six mortise sizes, each of which is a combination of two measurements. Once you know how to read the code, the six options stop being mysterious: they are simply the six commonest combinations we've found on the doors our customers own.
Reading the Code, Digit by Digit
Each code has two halves. The first two digits are the backset: the distance from the edge of the door to the centre of the handle hole. The last two digits are the centres: the distance between the two fixing points on the lock, which on every option in the push/pull range is 85 mm. So:
- 6085 — 60 mm backset, 85 mm centres. The Australian standard on hinged doors.
- 4585 — 45 mm backset, 85 mm centres. The European fitting.
- 3585 — 35 mm backset, 85 mm centres. Narrow aluminium stiles.
- 2885 — 28 mm backset, 85 mm centres. Narrow aluminium stiles.
- 3585 hook — as 3585, with a hook bolt for sliding doors.
- 2885 hook — as 2885, with a hook bolt for sliding doors.
| Code | Backset | Centres | Bolt | Typical door |
|---|---|---|---|---|
| 6085 | 60mm | 85mm | Straight | Australian hinged door |
| 4585 | 45mm | 85mm | Straight | European-style door |
| 3585 | 35mm | 85mm | Straight | Narrow aluminium stile |
| 2885 | 28mm | 85mm | Straight | Narrow aluminium stile |
| 3585 hook | 35mm | 85mm | Hook | Sliding door |
| 2885 hook | 28mm | 85mm | Hook | Sliding door |
💡 Did You Know?
The same four-digit code appears on every push/pull product, whatever the handle length or finish. A 6085 option on the long-handle SL-P1 and a 6085 option on the short-handle SL-P2 describe the same mortise — which is why you can choose handle, finish and mortise independently.
How to Measure Your Door
Step 1: the backset. With the door open, find the centre of the hole the handle passes through. Measure horizontally from the edge of the door — not the faceplate or the frame — to that centre. If you have the old lock off, the reading is the same. On a typical Australian hinged door you will land at 60 mm; on a narrow aluminium stile you will land well below that.
Step 2: the centres. If the old lock is still fitted, the faceplate on the door edge will show screw heads or the outline of the case; if it's removed, the pocket shows the case's footprint. Our range uses 85 mm centres throughout, so if your measurement is far from that, the door is one we should look at before you buy.
Step 3: the bolt. Is the door hinged or sliding? A hinged door takes a straight bolt, a sliding door a hook bolt. Our guide to hook bolt versus straight bolt explains why.
Step 4: the thickness. The SL-P1 publishes a door thickness of 45–70 mm. Measure the door at the edge and check that it falls inside the range for the lock you choose. For other models, check the thickness on the product page.
Step 5: the photograph. Take a photo of the door edge with the tape measure laid across the faceplate and the handle hole visible. It's the quickest way to confirm a measurement, and we'd rather look at a photo than have you guess.
✓ Six mortise options, IP66
Smart Door Lock — Long Handle Silver, IP66
Choose 6085, 4585, 3585, 2885 or a hook-bolt version — the code is on every option.
$494.99 AUD
View Product →Reading the Markings on an Old Lock
Many existing locks give you a head start. If you can take the old lock out, look at the case and the faceplate. Manufacturers often stamp a model or size on the case, and the faceplate shows the width and length of the pocket. These marks aren't a universal standard, so treat them as a clue rather than an answer, and always confirm with a tape measure. The point of measuring is that a door is a physical object: whatever the old lock says, the pocket in your door is the size it is.
The Mistakes That Cause Returns
Measuring to the wrong place. The backset is measured from the door edge to the centre of the handle hole, not to the edge of the hole and not from the frame. A few millimetres of difference is the gap between 6085 and 4585-style fits, which is why we ask you to be exact.
Mixing up backset and centres. Because the code is four digits, it's easy to read 6085 as "sixty-eighty-five" and wonder which half is which. The first two digits are always the backset; the last two are always the centres.
Assuming all aluminium doors are the same. Two narrow codes, 3585 and 2885, exist because aluminium frame profiles differ. Measure rather than assume, and check our guide to narrow aluminium stile doors.
Forgetting the handle. The mortise code says nothing about handle length. Choose the handle separately using our guide to long versus short handles.
Confusing centres across models. The lever and camera locks also use a number called centres, but with different values: the SL-H1 offers 147, 160 and 180 mm centres for narrow stiles, and the camera lock SL-C1 offers 147 to 240 mm centres with a 22 mm backset. Always use the figures on the product page of the lock you are buying; the 85 mm centres belong to the push/pull range.
| Your measurement | Likely option | Next step |
|---|---|---|
| Backset 60mm, hinged door | 6085 | Choose handle length and finish |
| Backset 45mm, hinged door | 4585 | Confirm centres are 85mm |
| Backset 35mm or 28mm, hinged door | 3585 or 2885 | Short handle is usually the fit |
| Backset 35mm or 28mm, sliding door | 3585 hook or 2885 hook | Check the frame keeper |
| Anything else | Not a standard match | Send us a photo with a tape across the edge |
✓ Same codes, short handle
Smart Door Lock Black — Push/Pull Handle
The short-handle version, with the same six mortise codes, for narrow stiles, framed glass and sliding doors.
$494.99 AUD
View Product →What If Your Door Doesn't Match?
Not every door has a standard mortise. Older doors, custom doors and doors that have been modified over the years can have pockets in unusual sizes, and some doors have no mortise at all — just a drilled hole for a cylindrical latch. In that case a mortise lock isn't a drop-in replacement, and the better route may be one of the lever locks, which are designed around the standard handle hole; our guide to lever handle versus knob covers that retrofit, and our backset guide explains its measurement. If you're in between, send a photograph and a tape measurement and we'll tell you honestly what we think. For framed glass, the framed glass door guide goes through the options.
Shop the Range
Push/Pull & Sliding Door Smart Locks
IP66 bar-handle locks — long and short handle, silver and black, with six mortise codes on every product.
Shop the Collection →For measurement diagrams, use the sizing guide, and compare every model in the complete buying guide.
Frequently Asked Questions
What does 6085 mean on a smart lock?
It is a 60 mm backset with 85 mm centres, and it is the Australian standard on hinged doors. The first two digits are the backset and the last two are the centres.
What is the difference between 6085 and 4585?
Only the backset: 6085 has a 60 mm backset and 4585 has a 45 mm backset, the European fitting. Both have 85 mm centres.
How do I measure the backset?
Measure horizontally from the edge of the door to the centre of the handle hole. Do not measure from the faceplate or the frame.
Does the code include the handle length?
No. The code describes the mortise inside the door. Handle length, long or short, is a separate choice, and every code is available on both.
What do the hook options mean?
3585 hook and 2885 hook are versions with a hook bolt for sliding doors, with 35 mm and 28 mm backsets and 85 mm centres.
What if my door matches none of the codes?
Send us a photograph of the door edge with a tape measure across it. Some doors have no standard mortise, and a lever lock may suit them better.
Key Takeaways
- Read the code as backset then centres: 6085 is 60 mm and 85 mm; every push/pull option has 85 mm centres.
- 6085 is the Australian standard, 4585 the European fitting, 3585 and 2885 the narrow aluminium stiles, with two hook-bolt versions for sliding doors — see hook bolt vs straight bolt.
- The code is the mortise only; pick the handle with long vs short handle.
- Measure first, using the sizing guide, the backset guide and framed glass door fit.
- Browse the push/pull range or compare models in the complete buying guide.