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 
consist of a rotating gear or rack with angled teeth. Pawls, which are sometimes misidentified as ratchets, are slim protrusions that rest against a ratchet to restrict its motion. When the ratchet is definitely rotated in one direction, the pawl is raised and moves smoothly between the angled the teeth. When the ratchet’s rotation stops, the pawl rests between the the teeth and makes a clicking sound. Ratchets and pawls that permit rotation in mere one direction cause the pawl and the teeth to clash if the ratchet is definitely turned the opposite way.
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.
