The Windsor knot, also referred to as a Full Windsor or a Double Windsor to distinguish it from the half-Windsor, produces a wide, symmetrical, triangular knot. It is often thought to be named after the Duke of Windsor but Was likely invented by his father, George V. The Windsor knot is especially suited for a spread or cutaway collar that can properly accommodate a larger knot. The Windsor knot is the only tie knot that is to be used by all personnel in the Royal Air Force and the Royal Air Force Cadets (ATC and CCF(RAF)) in the UK when wearing their black tie while in uniform. The Windsor and four-in-hand knots are authorized for use by all services of the Canadian Forces.