Abstract: A plurality of wide flat bus bars (A,B,C,N) stacked in flat face-to-face relation are clamped against separation forces of short circuit currents in the bus bars by U-shaped reinforcement channels (6,14) disposed over opposite edges of the bus bars with bight portions (6a,14a) of said channels abutting the edges of the bus bars and leg portions (6b,14b) thereof extending along flat surfaces of outer ones of said bus bars. A plurality of bolts (8) through aligned holes in outwardly directed flanges (6c,14c) formed on the free ends of the legs of the channels and are threadably tightened to draw the channels together and to exert a clamping force against the flat faces of the bus bars. A flat sided housing (16,24) is attached to the channels (6,14) and may be provided with access openings (16a) at intervals therealong for making plug-in connections with the bus bars.