Abstract: This invention provides a platform structure having a retractable floor portion consisting of four main floor panels extending outwardly in directions defining a cross, and pivotable between a horizontal and vertical position. There are also provided secondary floor panels for the quadrants between the main floor panels, the second floor panels being mounted to another main or secondary panel along aligned edges. The secondary floor panels can pivot through 90.degree. or 180.degree., to permit all panels to be folded into an upright position, to lie along a central framework portion.