A wall module (1') to be joined to other similar wall modules for forming larger wall assemblies is primarily intended to be used for the covering of lifts and lift shafts. The module has a first connecting portion (3) extending in parallel to a complementary second connecting portion (5). An intermediate portion (7) connects the connecting portions (3, 5) to each other. Thereby, the first coupling portion (3) has a cross section in the form of an arcuate tongue, the other one (5) having the form of an arcuate groove. Two wall modules (1') are joined by placing one wall module at an angle with an already mounted wall module (1'), the opening of said arcuate groove being placed over the tip of the tongue, the wall module to be mounted then being turned, so that the tongue penetrates into the groove until the desired position has been reached. Preferably, all members are manufactured from extruded aluminum.