Lock Case Numbers Explained: What 5845, 7255 and 8550 Mean

Updated 2026-11-05 · RAYEN 雷茵

Our lever handles list a Lock case for most models. That line tells you which mortise lock body the lever is built to work with. It is the most useful number on the page if you are matching a new lever to a door that already has a lock in it, and the easiest one to misread.

What do the first two digits mean?

They give the centre distance. You can check that on the plates themselves, where the drawing shows the distance from the lever to the keyhole.

5039-340 takes case 5045 and its drawing shows 50mm between lever and keyhole. 58150-704 takes case 5845 and its drawing shows 58mm. The same holds across the zinc alloy, aluminium and stainless plates in the table. The model number often says it too: 58150 and 5881 are 58mm plates, and 72150-704 and 7284-578 are 72mm plates.

Applied to the other codes, 7250 and 7255 read as a 72mm centre, 7855 as 78mm and 8550 as 85mm. Our 72mm plates confirm the first. For 78mm and 85mm we list no plate to measure, so take that reading to the lock-case drawing and check it.

What do the last two digits mean?

The trade reads them as backset: the distance from the door edge to the centre of the keyhole. That makes 45 and 55 a matter of how far the lever and cylinder sit from the door edge. Treat that reading as a starting point. Ask us for the lock-case drawing before you cut a door, and measure any lock you already have.

Why do some levers list two cases?

Because of where the keyhole sits.

• A long plate holds the lever and the keyhole in one piece. The centre is fixed in the metal, so the plate names a single case. Every long plate in the table above lists one code.
• A rose lever has no keyhole of its own. The cylinder gets a separate small cover, as the AL-114 photo shows, so the spacing comes from the lock case and the same lever can sit on either one.

So 8550 / 7255 on A5-653 means choose one of those two. It does not mean both come in the box, and a slash is not an order. The pairings follow the families:

• Zinc alloy rose and square-rose levers, such as A5-653 and A9-653: 8550 / 7255, door 38-50mm.
• Stainless steel 304 / 316 levers, such as S-01 and SF-15: 7255 / 7855, door 32-50mm. S-K210 and S-K401 list 7255 alone.
• Aluminium levers, such as AL-114: 5845 / 7250, with door 35-50mm where a range is given.

What do CF60 and CT60 mean?

These are letter codes, and the digit rule does not apply to them. Our list uses them on the BK and ET lever families, and their door ranges run thicker than the zinc rose levers.

CF60 is a lift-to-lock case: the lever is lifted to throw the lock. ET4017 uses it too. CT60 / 7255 means either of those two cases. ET4006A is one to look at closely, because its photo shows the key in the lever neck and no keyhole in the plate, so it can take two cases even though it has a plate. Confirm what the 60 stands for on the drawing.

Is K58 a 58mm centre?

No. The K codes belong to our concealed door locks, and here the printed 58mm is the backset.

A5-A002 has case K58, a backset of 58mm and a 23 × 78mm face plate. So do not run the four-digit rule on a code with a letter in front. A9-987 BL uses K55F, and its figures should come from its own drawing.

What should you measure on an existing lock?

• Centre distance: centre of the square spindle hole to the centre of the cylinder hole.
• Backset: door edge to the centre of the cylinder hole, at the face of the lock.
• Face plate: length and width, because the recess in the door edge has to match.
• Door thickness: it limits the lever, not just the lock. See lever handle door thickness.

If you are changing a plate as well, read lever handle plate sizes. The plate must cover what the old one covered.

What to write on your order

Name one case, not the slash: lever model, finish, lock case, door thickness, handing if the lever needs it, and quantity. For example: A5-653, matt black, lock case 7255, door 38-50mm. If you are matching a lock already in the door, send a photo of the case and the two measurements above. We will check them against our drawing before you order.