chain whip

A chain whip is a tool that will often be included in a decent bike tool kit. As the name implies, it has a long handle with a length of chain at the end. It is used as a way to grip the cogs of a cassette, allowing you to gain enough torque to loosen a lockring. Some older cassettes require the use of two chain whips applied in opposing directions to loosen the smallest cog of the cassette which itself acts as a lockring. Unfortunately, there are no real alternatives to a chain whip since using anything else will most likely screw up the cogs on your cassette. Luckily, if you have screw on type cassette, a chain whip is unnecessary.