Aluminium is a fascinating material with characteristics that make it especially useful whenever low weight, corrosion-resistance, strength, appearance or thermal or electrical conductivity are important. Extrusion gives it whatever cross-section is desired, which can incorporate a host of useful features. Tee-slots for holding nuts captive are one example, stiffening ribs another. Another point in favour of extrusion is cost. Extrusion dies are far less costly than those for moulding or casting, and can be produced in much less time. In addition, the process itself is relatively inexpensive to operation.