A percussion instrument, also called a noisemaker or cog rattle, that consists of a cogwheel and stiff wooden tongue in a frame. It produces a very loud clicking sound by spinning the cogwheel against the tongue.

The most common form has the assembly mounted on a handle, which rotates freely. The player holds the handle and swings the whole mechanism around, which makes the tongue click against the cogwheel. This style is.similar to a football rattle, which is sometimes used in its place when a particularly loud sound is needed. A popular design consists of a thick wooden cog wheel with two wooden flanges that alternately hit the teeth of the cog when the handle is turnsed. 

Alternatively, smaller ratchets are sometimes held still or mounted with a handle that can be turned rapidly by the player (as shown). The mounted ratchets allow for greater control of the duration and timing of the sound. This allows the ratchet to be used like a snare drum, placing sustained rolls in precise durations of time. Dynamics are controlled by the rate at which the ratchet is rotated.