Abstract: A modular display system is provided having a series of floor platforms which are secured together in edge-to-edge contact, by "plug-in" locks at the corners of two or more platforms. The locks engage floor frames below floor panels, through notches or cutout areas at the corners of the panels. Each lock engages at least two frames at their adjoining corners by downwardly projecting prongs, which preferably seat in the interior corner angles of the frames. The lock fits in the contiguous panel cutouts so that it is flush with the surface of the panels. Vertical columns may upstand from the locks, to support light boxes, shelving, tables, and the like.