Tobacco-drying ovens, also known as oasts, are used in the tobacco industry to dry and cure tobacco leaves. They are typically cylindrical in shape and have a conical roof with a vent at the top. The heat source is usually wood or coal, and the smoke from the burning fuel passes through the tobacco leaves, drying them out. Oasts are an important part of the tobacco-making process, as they help to create the desired flavor and aroma of the finished product.