Acrow prop

An Acrow prop is a piece of construction equipment. It is a telescopic tubular steel prop, used as a temporary support.
Acrow props are adjustable for height by a large diameter screw thread, formed on the outside of the tube itself. The screw thread provides a fine adjustment over a short range. A loose pin through a series of holes in the inner tube gives a wider range of coarse adjustment. Use of a screw thread also allows the props to be tightened when already in place, to adjust the load that each one bears.