Splits pins are known as a roll pins. Split pins are commonly used to fasten a shaft or similar component in place. It is a piece of flat spring steel that is rolled where 2 edges are almost touching where. When it is forced into a hole the spring tension holds it fast. They are also used to keep machinery aligned. The split pin is placed through a hole and the tines of the pin are then bent to hold the pin in place.
A split pin or a split roll pin is made from a harder grade of steel, such as spring steel. It is a narrow tube with a slit cut down one side. It is driven into a hole that intersects 2 parts, such as a pulley and a shaft. The hole is slightly smaller than the split roll pin. The pin compresses slightly upon installation and is driven in with a small punch, preferably a roll pin punch.
A split pin is a pin that once inserted through the hole has the ends turned back to prevent it from falling out. The split roll pin is the primary means of retention of the components. Without it, the components will separate.