in fig3 the rear wall comprises vertical stop lugs 41 a which enable two adjacent modules to be wedged together in the vertical direction with the bottom edge 42 of the top module resting on the stop lugs 41 a of the bottom module this arrangement avoids incorrect overlap of the edges of the modules moreover the vertical edges 43 and 44 of the modules 12 form fixing areas which are fixed onto the mountings 18 for example by screws 46 fig1 plates 47 serve as washers and trim for protecting the edges of the modules the mountings 18 here consist of wooden vertical uprights themselves fixed to the wall 20 by screws 48 as a variant the mountings are metal sections 18 a with a basically omega section fig2 a 28 b or metal sections 18 b with an open rectangular section fig9 a 29 b themselves fixed to the wall 20 by screws 48 the first variant will be chosen when adjacent modules have to be mounted overlapping each other but the second variant will be chosen when adjacent modules have to be mounted u2014 for whatever reason u2014 laterally spaced from each other in this case the width of the section 18 b must be determined in accordance with the desired spacing between the modules optionally the open section 18 b can be closed by a plate 49 shown in fig2 a by a dotted line according to a third variant shown in fig3 a 30 a the mounting is built into the modules in fact by forming in the front wall and rear wall fixing blocks 11.