Abstract: There is fixed, on a wall, a section member having a substantially U-shaped portion provided with an upper leg extended by a lug formed with a window adapted for setting in position an appropriate retaining member in a position chosen on the wall. A vertical central zone of the U-shaped portion is provided with an opening through which passes a rotatable retaining member having an inner screw thread and a front portion provided with a thinned-out zone adapted for retaining a nut. A threaded rod is screwed into the retaining member and terminates into a flattened portion through which extends a vertical channel adapted for receiving a pin that maintains by penetration a lower lining panel board and an upper lining panel board. A counter nut is provided to lock the threaded rod on the retaining member.

Abstract: Each spacer comprises a foot portion of a polygonal cross section, which is rotatably lockable in a correspondingly profiled part of the plate. Each foot portion is topped by a star shaped surface and extended by a vertical rod or column terminated by a head portion which is hollow for passage of fastening means provided for maintaining the upper fixation element onto the head portion. The upper fixation elements are suitably stiffened by corrugation means and provided with a center hole for passage of the fastening means.