Cotter Pins per ANSI/ASME B18.8.1
A cotter is a pin or wedge passing through a hole to fix parts tightly together. In British usage cotter pin has the same meaning, but in the U.S. it refers to a different fastener .
Typical applications are in fixing a crank to its crankshaft , as in a bicycle, or a piston rod to a crosshead , as in a steam engine. Note: the angle of the wedge determines the position of the parts being held, therefore on a bicycle the pedal arms will only be at 180 degrees to each other if the angle of the cotter pin's wedge is the same on both pins.