A tachi is a curved sword with a blade
length normally longer than 23.6" (60cm). These blades were made during the
Koto times and were worn with the edge down and suspended from two cords.
This is different than Katana which had the
sword worn on the belt and edge up. At the end of the Koto period many of
the tachi were shortened to katana length. To shorten a blade the nakago or
tang end is shortened. Many times shortened swords have the tip of the
nakago , called nakagojiri, squared off.
This squared off shape is called kirijuri.
There are many types of tachi mountings. The photo
above is of a type called Itomacki tachi, or "string wound" tachi. This is a
very common style.