A crescent-shaped tool with sharp points used in printmaking, especially mezzotints. The artist uses the rocker in a rocking motion to make marks all over the copper plate. The finished product usually has some of these marks polished or burnished so that they do not retain ink, and a positive/negative effect is achieved when ink is applied.Source:"Joel Oppenheimer" 35th Anniversary Catalogue, 2004, of the Natural Art Gallery