Lapping uses a loose abrasive and is applied to external surfaces, while honing is done on internal surfaces with bonded abrasives. Lapping is an abrading process that leaves fine scratches arrayed at random. Its purpose is to improve surface quality by reducing roughness, waviness, and defects to produce accurate as well as smooth surfaces. The lapping process is performed by hand and by machines. Honing is an abrading operation mostly for sizing and finishing round holes. To a lesser extent, it is used on external flat and curved surfaces by means of bonded abrasive stones. Micro finishing, also called super finishing or micro stoning, is generally done by scrubbing with an abrasive stone or stones pressed against a surface. Micro finishing is generally a second operation used to achieve superior surface finishes as well as eliminate minor surface defects (waviness, chatter, and feed marks) caused by grinding or other manufacturing processes. Roller burnishing cold works metal by forcing hardened, precision-ground rolls to rotate around the surface to be finished. Roller burnishing is used to finish straight and tapered holes, external cylindrical parts, and flat surfaces. A roller bearingizing tool works by simultaneously rolling and peening the surface. Polishing puts a smooth finish on surfaces and may often involve removal of appreciable metal to take out scratches, tool marks, pits, and other defects from rough surfaces. Final finish machining is one of the most labor-intensive and costly aspects of the precision parts manufacturing industry.