The adjustable base jack is the foot of a scaffold or shoring frame. A threaded steel stem runs through a nut and lets you level the frame on uneven ground. JBFS makes it with a 150 x 150 x 5 mm base plate, in six lengths. It is used with cuplock scaffolding. The stem is solid steel with roll threading and a malleable cast iron nut. The finish is red oxide paint or hot dip galvanised.