Metal extrusion is used to create lengths of metal of a fixed cross-sectional profile. Through extrusion, complex cross-sections can be created with excellent strength and surface finish. The process of aluminum extrusion works by forcing a block of metal, known as a billet, to pass through the die opening of smaller cross-sectional area than the billet itself. When the metal stock is heated and forces though the die is then shaped to the cross section of the die in desired lengths. This process is very accurate and produces little waste.