Ratchet is a hardened steel wheel, usually tempered straw yellow, which is located on the barrel axle but outside and on the barrel.

It is used to cock the barrel spring and is retained by a pawl and its spring on the outside of its teeth to maintain the energy accumulated in the barrel. In quality watches the ratchet is held by a pawl that always allows two to three teeth to pass before locking the force, thus minimizing the possibility of a defect called rebat.

Crown wheel is also made of hardened steel, and usually also turned straw yellow. It meshes between the ratchet and the winding pinion which is on the axis of the winding stem on which is fixed the crown that we see outside the case. The crown wheel is a wheel that has the particularity of being equipped with two teeth. One that meshes with the ratchet and the other with the winding pinion.