The chainsaw is driven by a two-stroke gasoline internal combustion engine connected via a transmission system (gearbox) to the saw chain. A closed roller chain moves along the guide rail and carries saw teeth. The chainsaw has an automatic clutch mechanism that works according to the centrifugal principle, thanks to which the circuit is stationary and safe at idle. If the load on the engine during sawing exceeds the permissible (for example, the chain is jammed), then the automatic clutch will break (or weaken to an acceptable level) the transmission torque to the tire and the engine will not stall. Modern chainsaws also have a brake mechanism that immediately stops the chain when the tire bounces towards the sawyer, an open circuit and other emergency situations. For some models, the tire is attached to the gearbox in such a way that it can be fixed in a horizontal or vertical position, which makes it possible to make cuts, respectively, in a horizontal or vertical plane. Many models of chainsaws, especially originally intended for use in felling, have the ability to connect an external hydraulic device (the so-called "hydrocline"), which is an executive hydromechanism. The injection of the working fluid (oil) into the hydromechanism is carried out by a chainsaw. Chain saws with an electric motor are widespread, and for example a mortar (a hand tool for selecting deaf narrow and deep nests) is only electrically driven.