Abstract: A multistation roll form machine for forming an article of complex shape such as a roof ridge vent having integral dams along the inner lateral edges of the ventilation panels includes a longitudinally extending support frame, a first group of individual roll forming stations, a lancing subassembly and a second group of individual roll forming stations. Each of the individual stations includes upper and lower roller die sets for continuously and progressively bending the stock material as it is fed through the machine. The first group of roll forming stations progressively bends the stock on itself to form dam portions integral with the lateral edges of the ventilation panels. The lancing subassembly positioned immediately downstream of the first group of individual stations, includes two pairs of outer and inner lancing rolls having teeth formed around their circumferences which lance the stock to form the ventilation openings.