A most important tool for clockmaking, having a serrated surface for removing metal by cutting and abrasion. Files are made in innumerable shapes and sizes and cuts, for many purposes. At one time almost all parts of a clock, including wheel teeth and pinions were shaped with files, and some files are named from the parts for which they were used, such as verge, pallet-wheel, endless-screw, pivot, etc. Common files are classified as flat, round, half-round, three-cornered, rat-tail, crossing and slitting, etc. , while types of cut are known as rough, bastard, smooth and dead-smooth. Clock sizes of files are made with a tang and should always be fitted in handles. A new file should preferably be used with brass until its keenness has worn off, when it becomes more suitable for iron and steel. The most common method of cleaning files is to brush them with a wire brush.