Abstract: Assembly comprises two parallel channel-shaped rails and pairs of jaws between the rails for gripping conductors extending transversely of the rails. Sides of one rail have external projections and the bottom of one jaw of each pair is also channel-shaped with its sides recessed to receive said projections with substantial tolerance. A spring is positioned between the channel-shaped bottom of the jaw and the mating rail which takes up the play due to the tolerance and electrically connects a grounding strip on the jaw to the rail.