The vortex block is a combined defensive technique of Gedan barai and Jōdan uchi uke. 

Manji uke is used almost exclusively in combination with Kōkutsu dachi. Areas of use are partner drills or Bunkai applications, based on a free-fighting stance. In the Kata, Manji uke appears very often. For the first time the technique appears in Heian godan. It is most often used in the Master Kata Gankaku.

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The Essence of Karate