Shapes of Japanese sword tang (nakago)
There are two and nearly equal parts to a Japanese sword, the polished blade and the
nakago. The tang or the part of the blade that goes into the handle (tsuka) or pole is called a nakago. The shape of the nakago and the style of filing has distinct features depending on the age and school of swordsmanship, making it just as important in the authentication process as the blade.
The nakago in many ways was the smith's personal domain. His signature resides in its curve, in its planes, in its ridges, in its finished edges and file marks, and in the shape as much as in the inscription itself. There are a variety of shapes of Japanese sword tangs (nakago) that vary in length, curvature, thickness.
Typical Ubu Nakago Form (Futsu Gata)
Futsu Gata is the most common type of nakago in both old and new swords, which occurs most frequently.
Kiji Momo (Kiji Mata) Gata
Kiiji Momo (Mata) means 'pheasant thigh'. This form of nakago is often seen on tachi (long swords) from the Heian and Kamakura periods.
This nakago form is characterised by its flattened lower portion. This shape of tang is commonly found in blades that are from the early 1800's and older.
Gohei refers to its resemblance to the pieces of paper which are attached to the sacred straw rope festoon used within Shinto shrines. This is only seen in the work of swordsmith Isenokami Kuniteru during the Edo period.
Funa means 'boat'. The nakago is so called because it is redolent of a boat shape. This tang style is commonly found in swords from the Showa period (World War Two) as well as older blades.
The Furisode form is so named because of its resemblance to the long sleeve of a young lady's kimono. It typically has strong sori and is usually found on shorter blades and tanto of the Kamkura period.
Tanago Bara Gata
Tanago Bara refers to similarity of this form to the belly of a particular fish.