Abstract: A plurality of struts extend upwardly from a subfloor and a plurality of racks interconnect selected rows of struts for supporting transmission lines and/or conduits. Each strut is formed of four orthogonally oriented C-channels having the edge of each leg curled inwardly to define a lip extending toward the base and each rack includes a similar C-channel. Each end of each rack is detachably attached to a C-channel of a strut by a bolt penetrating a plate at the rack end and threadedly engaging a nut captured in the C-channel of the strut. The transmission lines and conduits are secured to any of the C-channels of the struts and the racks by clamps having distal ends of two sections captured by the respective C-channel and an attachment mechanism securing the proximal ends of the sections to one another to retain the transmission lines and conduit clamped between the two sections.