Engraving was used extensively in the decoration of clocks, for dial centers, back plates, cases, hour, minute and second numerals, and the maker's name. Numerals when engraved were usually filled with black wax to give them visual clarity. The usual method of engraving is to gouge or chisel out the surface design by hand using a sharpened tool called a 'graver' or 'burin', or a chisel and hammer. Engraving can also be performed by machine using a form of milling cutter and an engraving machine fitted with a pantograph, which can accurately copy a design.