An expandable raceway for electrical wiring is constructed of a main section which defines a main passage. In cross-section the main section includes a leg and parallel arms that extend in the same direction from opposite ends of the leg. Each arm is provided with an indexing formation to receive a cooperating indexing formation along the free edge of an arm of an L-shaped auxiliary section for mounting the auxiliary section to the main section without dismounting from a surface to which it is already affixed or dismantling the main section. In cooperation with one arm of the main section, the auxiliary section defines an auxiliary passage outside of the main passage. The auxiliary section includes one arm parallel to the arms of the main section and one arm coplanar with the base of the main section and the latter arm includes the indexing formation thereon covers over the open sides of the sections. A splice connector may join the ends of adjacent sections and the connector is held in fixtures on the sections. The main section may have a divider supported along its length.

An end cap for closing one end of trunking, the end cap having a closure part for closing an interior space of the trunking and a fixing part for fixing it to a back of a base section of the trunking. The closure and fixing parts are connected together by a connecting part. The connecting part constitutes an elastic coupling which allows the closure part to move relative to the fixing part.

A prewired electrical distribution system of the type which may be fixed to and extend along a surface such as wall for distributing electrical energy is disclosed. The system employs relatively rigid conductor carrying members of various lengths interconnected by substantially identical relatively rigid couplers and may be easily and quickly assembled. Each of the relatively rigid conductor carrying members includes an elongated channel of relatively uniform cross-section throughout its extent with that channel being longitudinally divided into at least two separate raceways, one for receiving power carrying conductors and the other for receiving communication wiring. The channel is formed from two joinable, typically extruded plastic members, and one metal formed member adapted to be fastened, as by screws, to a wall or other surface. The first member is adapted to snap over the metal member enclosing the power carrying conductor raceway and forming a portion of the communication wiring raceway, and the second member is adapted to close the communication wiring raceway.

A compartmentalized electrical outlet box defines side-by-side forwardly open compartments for receiving power leads, data lines and telecommunication cables from inside a wall structure. These leads will be connected to corresponding conductors in a raceway that has at least two separated wireways defined in a base channel. Access openings are provided in staggered relationship at the rear wall of the raceway channel so as to be aligned with the compartments in the outlet box.

An accessory to be attached to a base section of trunking for routing electrical cables is provided with a wall for concealing, inside the trunking, any longitudinal gap beyond an edge of at least one length of cover section. The wall has an effacable projecting finger on the front. Applications include the fitting of electrical devices.