EC Lyons Rocker Weights are used to weigh rockers down. This makes the process of preparing a plate for mezzotint significantly easier, since it is not necessary to push the rocker down onto the plate.
Rockers are used to prepare metal plates for mezzotints. By repeatedly working the tool over the surface of the plate in a rocking motion, the printmaker can create a smooth carpet of burrs, which will hold ink and show up as a dark area when the plate is printed. This rough surface can then be smoothed with a scraper or burnisher, which will lighten the print in those areas.