Abstract: Support means for a workpiece, such as for example a printed circuit board to be screen printed, comprise a plurality of parallel upright elongate members, upper ends of which engage the underside of the workpiece or components secured thereon. Armatures and electromagneto magnets are provided in a housing selectively to clamp the elongate members in a raised position or allow them to fall to a lowered position.Clamping means to clamp the workpiece comprise clamping plates on opposite sides of the workpiece and having very thin foils projecting laterally therefrom over the workpiece and operating means to lower or raise the clamping plates to clamp or release the workpiece.