Castle nut has slots (notches) in the end, which look like castle. Castle nut design helps to lock the bolt or stud. Just use split pin or cotter pin, R- pin for safety and pass through the hole. Castellated nuts are used in low-torque applications, such as holding a wheel bearing in place.
Near Traditional Souq Market, Deira, Dubai, U.A.E
+971- 4- 388- 2753