Castle Nuts also known as slotted nuts have three notches in one end, giving an appearance similar to the crenelated battlements of a castle. They are generally manufactured in Steel or Stainless Steel, with other materials also available. These are positive locking devices that are used to ensure that the nut remains affixed and resists vibration. The bolt has one or two holes drilled through its threaded end. Castle Nuts are available in a range of sizes, at competitive prices.