Embusen

Embusen (演武線) is a Japanese term used in martial arts like karate and judo to refer to the spot where a kata begins, as well as its line of movement.

Though it is not stressed in Okinawa, nearly all Japanese-influenced kata start and end on exactly the same embusen point (Kiten).

So it is, for example, a straight line for the Shōtōkan Tekki series of kata.

For any kata, the embusen is fixed and must be followed exactly for proper mastery of the style.

The purpose of this is simply to allow the movements to be practiced in a small training space.