Made from U section, extruded aluminium with cast head and foot. Spring-loaded rapid adjustment mechanism sets foot to correct position on bar. Deep-cut Acme thread enables final tightening and application of clamping pressure. Made from U section, extruded aluminium with cast head and foot. Spring-loaded rapid adjustment mechanism sets foot to correct position on bar. Deep-cut Acme thread enables final tightening and application of clamping pressure.