Kenrick Excalibur Replacement uPVC Gear Box Door Lock Centre Case Single SpindleKenrick Excalibur Single Spindle Door Lock Gearbox A replacement centre case for the Kenrick Excalibur multipoint door lock mechanism. If you're having problems with your door lock, the gearbox is almost always the problem and changing it is as simple as removing a few screws. Kenrick Excalibur Gearbox Centre Case 35mm Information Important measurements: 35mm Backset 92mm PZ Centres This is the mechanism inside the door that is operated by the handle.