Abstract: At least two sections are arranged one behind another on a common integral substructure which is mounted on wheels, said sections being generally rectangular in plan and having vertical sides. Each of said sections is mounted on a pivot located in the central longitudinal plane of said common integral substructure, at least one of said pivots being longitudinally slidable in said substructure. Two sections are hinged together at one corner of each section, and are movable on their pivots, from a transport position in which they are longitudinally aligned with one another and with said substructure, to a transverse position of use in which a side of one section and a side of the other section, formerly in alignment, are folded together on said hinge.