Upon adsorption of Ag on 4° vicinal Si(001) the existing double steps form bunches with multiple step heights separated by flat (001) terraces. The step rearrangement is completely reversible and can be controlled by the adsorption temperature. Below 550°C an extremely regular array of 4-fold steps results. At higher temperatures the formation of a mixture of (115)- and (117)-facets, composed of up to 25 double steps has been observed. Using this method a regular series of flat and straight (001) terraces with an temperature controlled width of up to 100 nm could be generated.