Plain English Meaning

A small split pin you push through a hole in a bolt and then bend open so the nut can't unscrew itself in flight. If you take one out, you throw it away and fit a new one.

Full Definition

Small metal fasteners, usually a folded pin with two prongs, inserted through a hole in a bolt or shaft and then bent open to lock a castle nut, clevis pin, or similar fitting in place so it cannot rotate loose or slide out. On aircraft they are single-use safety devices: once removed and straightened, they are discarded and replaced with a new one.

Context Anchor

Seen during aircraft inspections and preventive maintenance when checking or replacing small hardware that must not loosen in .