The system has two modules for constructing counters. Posts are arranged at both sides of each module and support furniture elements (18) e.g. top and bottom shelves, of the modules and/or limit the modules. Each post has right and left partial profiles (30, 31) brought together to form an optical unit. The profiles are fixable together at its upper ends. The modules are different in shape, size or surface area, and all the profiles are identical to each other and have mirror-inverted design. Each post has same thickness independent of shape and size of the used modules.