A chainsaw consists of a small two-stroke gasoline (petrol) internal combustion engine (although smaller versions sometimes use electric motors), the "guide bar" (essentially a long metal frame of a very hard wearing alloy) and the cutting chain itself. Usually each segment in this chain (which is constructed from riveted metal sections similar to a bicycle chain, but without rollers) features a small sharp blade, called a "tooth."
Though chainsaws are popular in zombie video games and movies, they shouldn't be your first choice or any choice for that mater when choosing a weapon. In fact using one as a weapon is probably one of the worst ideas ever in a zombie infested world. Chainsaws require gasoline or a source of electricity to run, both of which may be hard to come by in a post-outbreak world. Also, chainsaws are very loud and the noise can attract more zombies. Another problem is weight, an average chainsaw weighs about 12 to 25 pounds plus carrying fuel or energy cells will weigh you down further compared to a gun that is around seven pounds. Why strain yourself even further then you need too? Save the fuel and energy cells for more important things like cars and running generators. Furthermore, chainsaws put the user at serious risk of accidental self-injury during a combat situation, especially if the chain flies off of the guide bar, which has already happened to too many lumberjacks before, not to mention the risk of infection by flying gores and bits produced when you are chainsawing through a zombie. Adding to the list of drawbacks, it is very loud and can attract even more zombies and other survivors, who may not let you live. It is important to note that chainsaws are designed for cutting through solid wood. While it will make short work of a skull, it is likely to get stuck inside the zombie and get caught in clothing. Therefore it is actually better as a blunt, unpowered weapon to be thrown from above like junk. Better to use it for it's purpose, cutting wood. Chainsaws may look intimidating to other survivors, but when it comes down to it you're better off with a knife or sword. The chainsaw is really best used as a last resort .