Castle Nuts (DIN 935)

Castle Nuts are made to DIN 935 and are often used alongside a bolt or a threaded rod that feature a pre-drilled hole, where a cotter pin can be used to secure the fixing and prevent movement.
These locknuts are also referred to as a Castellated Nut , and are ideal for use in applications where vibrations may undo a fixing.
Sometimes incorrectly, they are referred to as Slotted Nuts. Castle Nuts are a different fastener altogether. They visually look more like a Hex Nut and host protruding triangular portions, where as a Slotted Nut (pictured below), looks as though a Hex Nut has been cut with the slots and corners forming part of the protrusion.
This is a slotted nut.
Castle Nuts are generally manufactured in Steel or Stainless Steel, with other materials also available.
They are available in a range of sizes, with thin versions also available.
Non-standard sizes, materials and finishes are available to order as specials, including small volume manufacture, modifications and custom parts made to drawings.