Which fastener is used with cotter pin or safety wire?

• A. Castellated
• B. Wing Nut
• C. Rivet
• D. Non Metallic

Answer: (A)

Castellated nuts are designed to be secured with a cotter pin or safety wire. They have slots (castellations) and align with a hole in the bolt, allowing a pin to pass through to lock the nut against rotation. This setup prevents loosening in vibration-heavy environments, which is why cotter pins and safety wires are used with them. Wing nuts are tightened by hand and aren’t meant to take a cotter pin, rivets are permanent and don’t use pins, and non-metallic isn’t a specific locking method. So the one built to accept a cotter pin or safety wire is the castellated nut.