Chisel

Chisels are classified in different shapes according to different uses:

Flat Chisel: the cutting edge is flat, the cutting edge and the chisel body is an inverted isosceles triangle, mainly used for opening square holes or repairing some square holes;
Oblique chisel: the blade is 45° Angle, the blade and chisel body is an inverted right triangle, mainly used for repair, most of the dead corners for carving and carving repair;
Gouge: the cutting edge is semicircular, mainly used for opening circular or elliptical holes;
U type chisel: the cutting edge is U-shaped, which is rare now, mainly used for carving and repair;