Abstract: A trunking assembly for electrical cables comprises a channel section housing having a longitudinal opening defined by the inturned edges of its side walls. Mounting rails extend along the free edges of the inturned side walls within the channel section and a backing box for an electrical component such as a socket outlet is adapted to be fitted within the channel section and fixed to the mounting rails by a clamping ring. The assembly of the backing box and clamping ring is a snap fit within the housing and longitudinal adjustment of the assembly along the rails can be achieved prior to locking in position. When locked in position, the backing box and clamping ring improve the integrity of the housing by preventing significant deformation of the side walls.