The katana was more than a weapon to the Samurai of Japan. It was the representation of their soul and their commitment to society and the responsibilities that came with being a member of the warrior class. As such, the wearing, display and use of a katana required the observation of strict rules of etiquette and formality. Disrespect to a sword was considered an offense punishable by immediate execution. Martial arts practitioners today maintain these rules to preserve tradition.
The katana was worn thrust through the left side of the belt, edge up. This made the sword easier to draw and reduced the likelihood of causing damage to the inside of the sheath. In addition, it made the weapon accessible to the right hand--traditionally, left-handedness was seen as a sign of evil or lack of trustworthiness.
The Samurai rarely, if ever, carried a katana indoors. Instead, they left it near the entrance of a building in a sword rack specially designated for visitors or gave it to a servant of their host. Katana etiquette demanded that the sword be left outside to avoid antagonizing a host.
If a Samurai had to carry the sword over long distances without expecting to use it, he typically placed the sword inside a cloth bag. When the sheathed sword was carried in the hand for any reason, it was held in the right hand, hilt pointed behind at a 45-degree angle, edge turned upward. This indicated non-aggressive intent by making the hilt difficult to reach, and is still part of the process of bowing to an opponent in sword arts.
When the katana was not carried, it resided on a special rack known as a katanakake. This rack could be placed near the kamiza, or shrine, of a Samurai's house, or it could be placed at the Samurai's head during sleep. During wartime, Samurai kept their swords as close by as possible.
A katana should be placed on a rack edge-up with the hilt pointing left. This indicates nonaggression and respect for guests. If the samurai was in a hostile environment or expecting attack, the hilt of his katana could point to the right.
Several rules of etiquette exist concerning conduct in a dojo, or place of learning swordsmanship. When sitting in seiza, the formal kneeling posture with feet tucked under, place the sword to the right at the beginning and end of practice. Samurai who had to leave practice were expected to walk behind other students. Also, jostling or stepping over a sword was considered a serious breach of katana etiquette.
The katana was expected to remain in its sheath at all times unless its owner was drawing the sword intending to kill an enemy. Even touching the sheath or hilt when wearing the blade in the presence of another Samurai was considered a challenge to a duel. Also, in most cases asking to look at someone's katana was considered highly offensive and grounds for a duel.
JAPANESE SWORD SOCIETY OF HAWAII 2011