Sheets are cut using saws and rotary cutting equipment. Bandsaws and cold saws have mostly displaced them. They notched them to provide knives, graters and saws. Examples include welding equipment or metal chop saws. Some chains have safety features as safety links as on micro chisel saws. People armed themselves with pipes, hooks, steel rods, hatchets, saws, and machetes. Recently smaller cordless circular saws with rechargeable batteries have become popular. Sawmills use a crankshaft to provide a reciprocating motion to the saws. The high speed engine was widely used in sawmills to power circular saws. Metallurgy was a technique that allowed the use of saws and scalpels. Many higher end saws have gear-driven motors. Examples include chains on farm equipment, bicycles, and chain saws. Riving knife explains some of the hazards of table saws. NCOs and buglers carried axes, saws and billhooks. Two stolen circular saws and iron tacks were tried and found not to be bulletproof.