What is backset size / What backset size do I need?
The backset size on a lock or latch case is the distance from the edge of the door to the centre of where the handle spindle passes through the door (or the key / turn where applicable), this is dimension ‘X’ below. These measurements apply to all locks and latches we supply. Generally rules apply as follows: • For door knobs you need a minimum of 3″ case depth locks, we do however recommend 4″ or 104mm latches providing that these fit your doors. This is to prevent your hand from scraping on the door frame when closing the door. • Fire doors generally have a deeper frame rebate (overlap around the door!). This means you need a minimum of 3″ case depth locks. • When replacing old locks, the critical dimension is X as above, but this can vary by 3 to 4mm, so don’t worry if you are slightly out. This is needed to prevent filling and redecoration of the door.
