Chainsaws typically consist of a small two stroke gasoline internal combustion engine (although smaller versions sometimes use electric motors), the "blade" (essentially a long blunt metal frame) and the cyclic cutting chain itself. Each segment in this chain (which is constructed from riveted metal sections, much like a bicycle chain) features a small sharp blade. The motor drives the chain around the track at a high speed, providing a highly effective (if rather rough) cutting action.
Since their introduction, chainsaws have become a mainstay of forestry in the developed world. Despite numerous safety improvements, chainsaws can be highly dangerous, and injuries arising from their use are relatively common. The most common accident arises from "kickback", when the saw blade stalls (due either to being bound by the wood or by striking a resilient object) which causes the entire saw to jerk uncontrollably. Kickback frequently results in serious injuries or death. The risks associated with chainsaw use mean that extensive protective clothing is generally worn while operating them, and many jurisdictions require that operators be certified or licenced to work with chainsaws.