Abstract: A method and an apparatus for the fabrication of a metal cylinder from a flat metal sheet is described. The cylinder is preferably, but not exclusively, for use in the construction of an outer casing for a hot water heater. Particularly, the method and apparatus is suitable for the fabrication of cylinders of different diameters with minor adjustments being necessitated to the assembly apparatus. A flat metal sheet is fed through a roll former where a curved sheet defining an unconnected cylinder having opposed overlapping free side edges is formed. Flanges are formed along the elongated edges of the cylinder with the flange of the outer overlapping edge being inturned and the flange of the inner overlapping edge being outturned.