The cepezed construction system that is most frequently applied is the modular system for the Primafoon telephone shops. To help realize the rapid and smooth revamp of sixty telephone shops in existing shopping premises, a layout system was developed consisting of a meccano box of prefab and powder-coated steel components.The shop that is to be revamped is completely emptied. The new layout is actually a climatized box in the existing space. Only the necessary new façades need to be specially designed for each shop. The new walls and ceilings are made up of a prefab system of portals that consist of perforated and set-steel ridged plates with steel wall and ceiling panels between them. All the necessary pipes and ducts have been built into the system. Various types of suspended panels have been developed. These can easily be replaced by panels with cupboards, racks or shelves. As a result, each shop can be laid out for variable use. The perforation of the steel frames and the panels has been implemented by making use of a computer, so that a great degree of dimensional stability has been achieved.