How To Correctly Measure A Sash Lock

There Are Six Measurements In Total.

No. 1: the backset

No. 2: the centre

No.3: the faceplate(or “forend”) length

No.4: the faceplate(or “forend”) width

No.5: Case width

No.6: Case height

The most critical measurement is the center and the backset, as both are the critical size for installation. Followed by is the size of the forend, or “faceplate”, although the forend usually is hidden when the door is closed, out of aesthetic purpose, it is still be considered as the least important measurement.


You, Will, See All 6 Measurements As Displayed In The Diagram.

A – The case width

The case width is commonly referred to as the block size”. There are many different case widths.

B – The backset

The backseat is a very important measurement. It is the distance from the centre of the keyhole( or the cylinder hole), to the leading edge of the lock.

C – The Case Height

The case height depends on the specification and manufacturer of the lock.

D – The “Centres”

Similarly to the backset, the centre measurement is very important.

The center is the distance between the center of the follower (the square hole the spindle passes through for door handles) and the center of the rounded part of the keyhole(or the cylinder hole).

E & F – The Faceplate / Forend Size

The faceplate size is the width and height of the faceplate. This is visible on the edge of the door once fitted.

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