Abstract: A skeleton structure for a free standing wall type or a gondola type fixture assembly, comprising modular base units secured successively to each other as a base structure by uprights of framing for selectable superstructure. A modular primary base unit, of generally hollow rectangular plan form, fabricated with inward top and bottom flanges from sheet-metal shallow channel stock, with the channel vertical web providing panel-like unit sides, has like vertical half-sockets of rectangular cross-section located on respective central webs of two opposite sides, with the top flange notched above each half-socket, the half-sockets being located centrally of the base sides for island fixtures or at back corners of half-base units for wall type fixtures.