Abstract: Multi-aperture ventilated floor members, for use in a grain bin or like applications, are formed from continuous sheet metal strip stock, complete, in one pass through a cold roll forming machine, in a method in which the critical steps comprise roll-lancing the metal strip to form multiple closed slits transversely of the length of the strip and then roll corrugating the strip transversely of its length to widen the slits into narrow open ventilation slots by stretching the metal, simultaneously ironing out the projections formed when the slits are lanced into the strip.