Lock Shop Direct measurement guide
How to Measure a Cylinder Lock Case
Use this guide to identify and measure a cylinder-operated mortice lock case, including euro and oval profile sashlocks, deadlocks and latch cases.
Important: A matching backset and case size do not guarantee compatibility. The cylinder profile, function, spindle arrangement, latch and bolt positions must also match.
1. Identify the cylinder profile and lock function
Cylinder-operated mortice lock cases are available for different cylinder profiles and functions. Check whether the case accepts a euro profile, oval profile or another cylinder, and whether it is a deadlock, sashlock or latch case.
2. Measure the lock case
The key measurements normally required are the backset, case depth, case height, centres and forend size. Product pages may use slightly different labels, so compare the diagram as well as the written size.
| What to check |
How to measure or identify it |
Record |
| Backset |
Front edge of the forend to the centre of the cylinder cut-out or spindle centre line. |
_____ mm |
| Centres (PZ) |
Centre of the handle spindle to the centre of the cylinder. |
_____ mm |
| Case depth |
Rear of the forend to the back of the lock body, excluding the forend. |
_____ mm |
| Case height |
Top to bottom of the lock body. |
_____ mm |
| Forend |
Length, width, end shape and fixing-hole positions. |
________ |
| Spindle follower |
Square spindle size and number of followers. |
_____ mm |
3. Match the latch, bolt and cylinder operation
- Latch only, deadbolt only or combined sashlock.
- Latch handing and whether it can be reversed.
- Deadbolt throw and the position of latch and bolt relative to the spindle.
- Euro, oval or other cylinder cut-out.
- Cylinder cam or actuator required by the lock case.
- Single, split or dual spindle arrangement.
- Escape, classroom, storeroom or other special function where applicable.
Two cases with the same overall size can operate differently. Check the manufacturer’s function description and cylinder compatibility.
4. Check the door, keep and furniture
Record the door thickness, handle type, cylinder length and the dimensions of the existing keep. If the door is rebated, note the rebate depth and whether a matching rebate kit is fitted.
Check that the fixing screws for the handles and cylinder furniture do not clash with the lock case or its internal mechanism.
5. Final comparison before ordering
Model-for-model replacement is usually safest
Where the manufacturer and product number are visible, search by those details first. If using an alternative, compare the full technical drawing, not only the backset and centres.
- Profile and function match.
- Backset and centres match.
- Case and forend fit the existing preparation.
- Latch, bolt, spindle and cylinder operation match.
- Certification is suitable for the door and application.
Still not sure which product you need?
Send our team clear photographs and your measurements before ordering. Please include:
- Front and rear photographs of the complete lock case.
- A clear image of the cylinder cut-out and spindle followers.
- Backset, centres, case depth, case height and forend dimensions.
- Latch and deadbolt positions and any special operation.
- Manufacturer, model number and markings.
This guide is intended to help identify and measure replacement hardware. Product designs, terminology and handing conventions can vary by manufacturer. Always compare the complete product specification and fitting instructions. Where a door or fitting forms part of a fire escape, fire door, powered system or other safety-critical installation, obtain advice from a competent person before ordering or altering the hardware.