Tooth plate: the part of a bicycle on which the axle is connected to the crank. The athlete drives the crank by pedaling, then drives the toothed plate to rotate, and finally drives the rear wheel to rotate through the chain and flywheel to provide power, thus completing the whole transmission chain of the bicycle.

Number of gear plates on the tooth plate: there are three types: single, two and three. There is hardly any four pieces, because it is technically difficult and actually meaningless.