Abstract: The device comprises a generally L-shaped angle plate or base plate bearing a first jaw on the shorter leg of the "L", fixing plates and a slider capable of being shifted along the base plate and bearing a second jaw. The base plate is fixed at three points to fixing plates and is adjustable with respect to the fixing plates by means of vertical adjusting screws mounted in the base plate and acting upon supports movably resting against the fixing plates. Side or lateral adjusting screws acting against a pin attached to one of the fixing plates permit the base plate to effect a limited angular displacement about a ball disposed in the region of the base plate defined by the intersection of the legs of the "L". The device permits an accurate positioning and orientation of a workpiece relative to the wire of a spark erosion machine and to the direction of this wire in its working position.