Glossary of Judo terminology
Jonai / Jogai (Inside / Outside contest area)
The Kodokan rules call for a contest area which is 14.55m square, with another square of 9.1m centered within the larger square. 50 tatami mats are placed within this inner square area, with other mats or tatami mats being placed in around the inner square's 2.73m outer perimeter. A red boundary line (approx. 90cm wide) surrounds the contest area to clearly demarcate this area from the outer perimeter area. The contestants' tactical maneuvers often unfold on this red line area.
Although a Waza applied outside the contest area is invalid, the "in" or "out" judgment is made by the judges. The criterion for an "out" judgment varies according to the Waza being applied:
For a Tachi-waza (Standing techniques), an "out" judgment is made if a leg of the contestant applying the Waza is outside the red line. For a Sutemi waza (Sacrifice techniques), an "out" judgment is made if more than half the body of the contestant applying the Waza is outside the red line. For a Ne waza (Ground techniques), an "out" judgment is made if the entire bodies of both contestants' are outside the red line. However, the above may not apply if a Waza is judged as "in process". (Article 5 of the Kodokan Judo Competition Judgment Rules; Article 9 of the International Judo Federation Competition Judgment Rules.)
* The contest area size varies somewhat in international competitions.