Abstract: A pressure assembly comprises a base plate, a ram and a wedge located between the base plate and the ram, the wedge having an inclined face facing the base plate or ram, the facing surface of the base plate or ram being inclined at the same angle and a screw adapted to move the wedge at right angles to the separation of the ram and base plate to alter the separation of the ram and base plate. Preferably a pair of wedges are provided, and preferably their inclined faces are oppositely-inclined. The pressure assembly may be used in conjunction with a support member adapted to be secured to a firm foundation, for example by bolts passing through bores. The assembly can be used to clamp a workpiece between the ram and a fixed member by engagement of the base plate with the fixed member and by increasing the separation of the ram from the base plate by rotating the screw.