R-clip

R-clips are commonly used to secure the ends of round shafts such as axles and clevis pins.

This angled end rides the side of the shaft and opens the "belly" mouth enough to pass the widest part of the shaft as the R-clip is inserted.

There is also a double loop variety when a wider range of suitable shafts is required, and to facilitate the attachment of a retaining tether to prevent the pin's loss when removed.

R-clips are similar in function to split pins and linchpins.

Compared to split pins, they are easier to remove and are re-usable.