Japanese swords differ in the length of their blades and in their mounting. Long swords, with a blade length over 610 mm (2 shaku,尺), were worn in the medieval period slung edge downwards, and called tachi.
This was the only long sword mount in earlier times, and was retained during the Edo period for wear with armour or at court. Daggers called tanto, with blades less than 305 mm (1 shaku) long were traditionally worn with tachi.
The katana mount, designed to be worn edge upwards and thrust through the sash, gained popularity during the 16th century as bushi increasingly fought on foot rather than horseback. It became the standard sword for wear with civilian costume, and was paired with a shorter sword similarly mounted, called a wakizashi with a blade between 305 and 610 mm in length.
A pair of swords with matching mounts was known as a daisho. Merchants, artisans and others of more lowly rank were only permitted to wear a short sword or a dirk.
As the signature of a sword was always on the outside ( omote 表), as worn, blades are described as being signed katana-mei or tachi mei.