Abstract: A cable tray has a pair of opposed side rails with a pair of aligned through bores. One or more stacked cable support blocks extend between the opposed side rails. A lower rung extends between the rails at the pair of aligned through bores. The lower rung has an upwardly opening channel extending along its length receiving the bottom edge of a lowermost one of the cable support blocks. The lower rung also has at least one opening extending through the lower rung in alignment with the pair of aligned through bores. A fastener extends through at least one opening of the lower rung and through at least one of the pair of aligned through bores in the side rails.