ELECTRICAL DISTRIBUTION APPARATUS COMPRISING SHEET METAL SECTIONAL DUCT RUNS CONTAINING CONDUCTORS AND COVERS; ELECTRICAL DISTRIBUTION APPARATUS COMPRISING SHEET METAL DUCT RUNS CONTAINING NAKED BUS BARS AND PROVIDED WITH APERTURES PROVIDING EXTERNAL ACCESS THERETO, AND ALSO PROVIDED WITH LARGE AREA MOVABLE COVERS, THE APPARATUS FURTHER INCLUDING FUSED PLUGS HAVING PRONGS ENGAGING SAID BUS BARS AND PLUGGED INTO HOLES OF THE CONDUIT, THE CONDUIT HOLES BEING SEALED AT ALL TIMES BY MOVABLE COVERS THEREFOR, OR BY SAID PLUGS; ELECTRICAL DISTRIBUTION APPARATUS COMPRISING DUCT RUNS CONTAINING BUS BARS AND PROVIDED WITH ELONGATED SLOTS THROUGH WHICH MAY RIDE PORTIONS OF TROLLEYS, THESE HAVING CONTACTS ENGAGING THE BUS BARS AND RIDING THEREALONG AS THE TROLLEYS ARE MOVED ALONG IN THE DUCTS