Tameshigiri

Tameshigiri (試し斬り, 試し切り, 試斬, 試切) is the Japanese art of target test cutting. The kanji literally mean "test cut" (kun'yomi: ためし ぎり tameshi giri). This practice was popularized in the Edo period (17th century) for testing the quality of Japanese swords^[1] and continues through the present day.

During the Edo period, only the most skilled swordsmen were chosen to test swords, so that the swordsman's skill was not a variable in how well the sword cut. The materials used to test swords varied greatly.

In modern times, the practice of tameshigiri has come to focus on testing the swordsman's abilities, rather than the sword's. Thus, swordsmen sometimes use the terms Shito (試刀, sword testing) and Shizan (試斬, test cutting, an alternate pronunciation of the characters for tameshigiri) to distinguish between the historical practice of testing swords and the contemporary practice of testing one's cutting ability.

The target most often used at present is the goza or tatami "omote" rush mat. To be able to cut consecutive times on one target, or to cut multiple targets while moving, requires that one be a very skilled swordsman.
Targets today are typically made from wara or goza, either bundled or rolled into a tubular shape. They may be soaked in water to add density to the material. This density approximates that of flesh. Green bamboo approximates bone.

When cutting a straw target that is standing vertically, the easiest cut is the downward diagonal.
Next in difficulty is the upward diagonal cut which has the same angle, but works against gravity and uses slightly different muscles and rotation. The third in difficulty is the straight downward cut, not in terms of the grain but in terms of the group of muscles involved. The most difficult cut of these four basic cuts is the horizontal direction (against a vertical target) which is directly perpendicular to the grain of the target.