The present invention provides a clamp for holding a workpiece that is particularly suitable for use in CNC machining. The clamp is particularly useful for use in picture-frame machining techniques as it allows a workpiece to be held in a position wherein a machine can have substantially unencumbered access to both sides of the workpiece without the need to remove the workpiece from the clamp. The clamp comprises a frame comprising a base, a first arm, and a second arm, the first arm and the second arm each mounted to the base at an inner end such that they are parallel with one another.