An attachment for a builder's prop, scaffold pole of the like comprising a stem screw-threaded along at least a portion of its length and provided at one end with a top bearer plate, an intermediate bearer plate being mounted on a tubular sleeve which is slidable along the stem and adjustably positionable thereon by means of a nut engaging the screw thread, means being provided for preventing rotation of the sleeve around the stem as the nut is rotated to alter the position of the sleeve along the length of the stem.