We value simplicity here at Home Secure. No matter how technical or difficult a job may seem we like to get it down to the fundamentals for ourselves and for our customers. Replacing a multipoint uPVC door lock may seem like a daunting task but with the right tools and know how it is relatively simple.

Always try and replace your old gearbox with the exact same size and brand.

The Tools

All you need to replace your old uPVC mechanism with a new central gearbox is a screw driver or drill and a spare 5 minutes! As long as you have selected the correct size central gearbox you will have no difficulty in changing it over. For the professionals or expert DIY members among you it is a good idea to test out your handy work to see if your uPVC lock is functioning correctly. To do this it is always good to have a locksmith’s multipoint operating tool handy.


The main measurement you should be looking for on your uPVC gearbox replacement is the backset. The backset is the part of the mechanism that will be placed within the composite door. The depth of the backset can be measured from the edge of the gearbox case to the centre of the euro profile. The second measurement you need is the PZ measurement, this goes from the central euro profile to the top of the spindle.

See Fig.1 for the backset size and Fig.2 for the PZ size:

To see how to quickly and efficiently change over your old uPVC door lock with a new replacement central multipoint gearbox then take a look at our ‘uPVC Door Lock Multipoint Change Over’ video below: