Jesus nut is a slang term for the main rotor retaining nut[1] or mast nut, which holds the main rotor to the mast of some helicopters. The related slang term Jesus pin refers to the lock pin used to secure the retaining nut. More generally, Jesus nut (or Jesus pin) is used to refer to any component that is a single point of failure and whose breakdown would result in catastrophic consequences, the suggestion being that in such case the only thing left to do would be to pray to Jesus, or that the component's importance could be likened to the importance of Jesus to Christianity.