Abstract: To assemble pieces of furniture, for example shelves, hollow supporting shapes (1, 2, 3) having a rectangular cross-section are connected by means of Lshaped angle braces (4) and tenons (5) which can be inserted into the ends of the shapes so as to form frames (19, 21), and assembled into cubic pieces of furniture using said shapes (3) as upright posts. According to the invention, frame shapes (23) having four chambers are preferably also used, which can save as the resting edges for shelves (22). These frame shapes (23) have a slot (36, 37, 38, 39) for each chamber, in which slots sliding door elements (33, 34) of different thicknesses can be held by means of an elastic shape (35) in such a way that the doors can easily be displaced. Said elastic shapes (35) preferably comprise grooves (36, 37, 38, 39) of different thicknesses for receiving the sliding door elements (33, 34).