Components & reference points
The lock backset
The shaft is a horizontal dimension essential for identifying a lock. On an in-situ lock, it is measured from the face of the faceplate to the centre of the operating mechanism as indicated by the manufacturer.
THE KEY POINT TO REMEMBER
The backset is measured horizontally. The centres measurement is the distance between two centres, usually the handle spindle and the cylinder.
Why this measurement matters
Two locks that look similar can have different axes. This dimension determines, among other things, the position of the handle and cylinder relative to the edge of the door.
An incorrect measurement can make a replacement incompatible with the existing holes. It may also leave too little room for the door furniture or require alterations to the door.
How to take the correct measurement
On an open door, identify the faceplate visible at the edge. Measure perpendicularly from this plate to the center of the handle follower or cylinder, according to the technical plan.
Do not take the outer edge of the handle as a reference. On some cabinets and rim locks, the measurement reference varies: the manufacturer's drawing remains the best way to confirm the dimensions.
Backset, centres and lock case dimensions
The handle-cylinder set-back is measured vertically between the centres of the two handles. It does not replace the measurement of the shaft.
When ordering a lock, also note the height and depth of the cabinet, the faceplate width, its ends, the position of the fixings, and the handle spindle dimensions. A photo of the old reference helps with identification.
In case of replacement
A lock with correct dimensions often allows the retention of the handles and existing holes. Compatibility must still include the direction of opening and the operation of the bolts.
A forced mechanism should not be compensated by excessive tightening. The housing, fixings, and strike plate alignment must be checked before concluding a fault.
MULTISECU ADVICE
Uncertain about your lock?
A photo of the mechanism, along with some details about your door: we help you identify the right solution.