A steam-jacketed kettle is similar to a double boiler and cooks large quantities of food by using steam heat. It is designed with both an inner and outer steel wall that cooks the contents inside by releasing steam into the space between the walls. These devices are often used to cook foods like stock, gravy, sauce, or soup, and may be powered by electricity or gas. They come in various sizes, for installation on the floor, countertop, or wall. Steam-jacketed kettles are often used in restaurants and industrial kitchens, where very large amounts of food are prepared daily.