Shell sections were made from flat rolled plate, of thickness typically in the range 18-25 mm. The plate was cold-rolled to the required curvature, typically into semi-circular pieces. Two of these were then joined to make a cylinder, usually of length about equal to the diameter. The pieces were butt-jointed together using a strap of steel plate of similar thickness attached with rivets. The cylindrical sections were joined end-to-end in a similar manner. Short sections were usually assembled at the factory, and final assembly was performed on site, with the kiln in place.