N.Knot_Structure -- A .Knot_Structure includes the .Knot (the part which has a gripping function) plus any by-products such as the .Tail_End and .Rings and so on. It also includes any external objects which are required for the .Knot's gripping force (as in the case of a Clove Hitch, for example). ".Knot_Structure" is often shortened to ".Knot" for simplicity (e.g. when we say that a Bowline and a Sheet Bend are two different .Knots, but we really mean that they are two different .Knot_Structures).