Kenrick Excalibur Replacement uPVC Gear Box Door Lock Centre Case Double Spindle. This is a replacement centre case for the Kenrick Excalibur multipoint door lock gearbox. It features a 35mm backset and 92mm PZ centres, making it the mechanism inside the door operated by the handle. It is likely the part to blame when a lock fails. This gearbox is reversible for both left and right-handed doors and has a double spindle for lever/lever and lever/pad operation. Manufacturer: Kenrick.