Installing Slim Series on Non-Multipoint Doors – Choosing the Correct Mortice Size

Many doors are not originally designed with a multipoint or lift-to-lock mechanism. If your door is one of these, you can still install a Slim Series smart lock, but the door will need to be adjusted with a suitable mortice lock.

Choosing the correct mortice size is important because it determines where the handle spindle and cylinder will sit in the door.

Below is a simple guide to help you identify the correct size.

Understanding Backset (The Most Important Measurement)

When selecting a mortice lock, the most important measurement is the backset.

The backset is the distance from the front plate of the mortice lock to the centre of the spindle (the square hole where the handle goes).

Common backset sizes include:

• 35mm
• 45mm
• 55mm
• 60mm

This measurement determines how far the handle and lock sit from the edge of the door.

When adjusting your door for a Slim Series lock, choosing the correct backset ensures everything aligns properly.

Understanding the PZ Measurement

Another measurement you may see when looking at mortice locks is the PZ measurement.

The PZ is the distance between:

• the centre of the handle spindle
• and the centre of the euro cylinder keyhole

Typical PZ measurements include:

• 72mm
• 85mm
• 92mm

Most Slim Series locks have a fixed lower stub at 85mm, but thanks to the design of the keyhole, they can still work with doors ranging approximately from 72mm to 92mm PZ.

Why the Correct Mortice Size Matters

When installing a mortice lock, the holes for the handle spindle and the cylinder must be drilled in specific positions.

These positions depend entirely on the backset measurement.

If the wrong mortice size is used:

• the holes in the door may not line up correctly
• the smart lock may not fit properly
• additional drilling or adjustment may be required

This is why identifying the correct mortice size before installation is very important.