The flat chisel, like the point and tooth chisels, is a metal hand-held tool which is struck with a metal hammer, or wooden mallet in some cases. It consists of a shaft, 15-25 cm long and 1-2 cm in diameter, with a flat and sharpened cutting edge perpendicular to the line of the shaft. The width of the cutting edge can vary significantly, between 0.5 and 10 cm; the wider varieties are sometimes called bolsters or droves. Further variation is found in the profile of the corners of this cutting edge. Sometimes they are rounded so that they do not catch on anything during delicate work but often they are left squared and sharpened for the careful application of detail and especially for letter-carving.