The adjustable stirrup head, also called an adjustable U jack, sits at the top of a prop or scaffold. Its U-shaped head holds the formwork or span, and the threaded rod lets you set the height exactly. JBFS makes it with a 100 x 5 mm U-head and a roll-threaded rod, in six lengths. The rod carries a malleable cast iron nut, and the finish is red oxide paint or hot dip galvanised. It is used to connect formwork and span to the supporting structure in building and bridge work.