this invention relates to a machine for and a method of making building products from a coiled sheet of thermoplastic polymer such as polyvinyl chloride . in the practice of this invention , portions of the polymeric sheet are selectively and sequentially heated and progressively bent to the desired shape by passing the sheet through a series of heating , forming and cooling stations . the simplified design of the machine enables the user to custom fabricate building products at a construction site with a resulting savings in cost . typical products adapted to be made in accordance with the invention are exterior building siding , siding accessories and other building products .