This British Standard specifies requirements for boxes for flush mounting of electrical accessories in a wall, or other flat surfaced structure to ensure interoperability. It is applicable to boxes for the mounting of electrical accessories with a rated voltage up to and including 440 V.This standard specifies requirements for boxes made from metal and for boxes made from non-metallic materials.This standard also specifies the mounting lugs necessary for mounting the electrical accessory in the box and the fixing holes necessary for fixing the box to the surface to which it is to be attached. This includes the position and numbers of accessory fixing lugs, requirements for M3.5 threaded fixing holes for the mounting of electrical accessories and provisions for lugs allowing angular adjustment of the accessory with threaded M3.5 holes for accessory fixing.