Extruded aluminum is made by heating the aluminum and forcing it through a die. What comes out on the other side is the shape of the final product. To visualize the process, imagine pushing a ball of clay through a circle punched with holes. What comes out on the other side is a series of spaghetti-like strands. The shape of the die determines what the final product will look like. For example, an "I" shaped die creates aluminum I-beams. After the product comes out of the die, it is cooled and then stretched to remove any twisting that occurs during the cooling process. As it hardens, extruded aluminum becomes stronger. The hardening process can take place at room temperature, but since that can be time consuming, most manufacturers employ heated rooms to temper the aluminum quickly.