Ratchets and pawls are mechanical assemblies that are accustomed to transmit intermittent rotary movement, or to permit a shaft to rotate in a single direction but not the other. Ratchets and pawls are usually made of:
steel
stainless steel
cast iron
brass
other metal materials
Features
Ratchets are sometimes called ratchet wheels because they 
Pawl
Applications
Applications for these single-direction devices include:
Pawls For Ratchets Wheel turnstiles
spanners
winders
jacks
The action of a ratchet could be either severe or smooth, depending on the configuration of the ratchet teeth and pawl.
