A ratchet is a mechanical device which Ratchets Wheel allows continuous linear or rotary motion in mere one direction while preventing motion in the opposite direction. Ratchets are widely used in machinery and tools. A rachet contains a round gear or a linear rack with the teeth, and a pivoting, spring-loaded finger known as a pawl (or click, in clocks and watches[1][2]) that engages the teeth. The 
teeth are uniform but asymmetrical, with each tooth having a moderate slope using one edge and a much steeper slope on the other edge.
When one’s teeth are relocating the unrestricted (i.e. forward) direction, the pawl easily slides up and over the carefully sloped edges of the teeth, with a springtime forcing it (often with an audible ‘click’) into the depression between your teeth as it passes the tip of each tooth. When one’s teeth move in the opposite (backward) direction, however, the pawl will catch against the steeply sloped advantage of the 1st tooth it encounters, therefore locking it against the tooth and avoiding any further motion for the reason that direction.
Specifications
Angle of teeth 60°
Material S45C
Heat therapy Induction hardened teeth
Tooth hardness 50 ～ 60HRC