Jaw plates for removably attaching to the jaws of machine vises extend above the top of the jaw to hold taller workpieces. They are made from aluminum alloy for readily machining to conform to contours of a workpiece not easily held by flat jaw faces. They are sections cut from a special extrusion for enhanced physical properties and economy of production. Through holes are drilled for fastening to the jaw face. The plate has a planar vertical face for lying flat on the vertical jaw face. A second face engages the top horizontal face of the jaw. A groove between the two plate faces ensures the second face engages the horizontal face of the jaw away from the intersection of the faces. Alternatively, material on the plate may conform to the workpiece when hot and retain shape when cool.