In the "introduction to Zazen"... Sawaki Roshi [ states that] " ... . First you should know the difference between two ways of sitting: G˘maza, the "posture that subdues demons", and kichij˘za, the "auspicious posture". Even in old texts, there is quite some confusion about the two postures. In short, the right side represents the ascending, active (yang) aspect. The left side represents the descending, passive (yin) aspect. When the right foot rests on the left thigh, that represents the ascending activity that subdues the demons (g˘maza). When the left foot rests on the right thigh, that is a descending, passive activity which is auspicious (kichij˘za).
You might think that this is only true for the half lotus. But that is not the case: In full lotus as well, if you first place your right foot on top of the left thigh, that is called g˘maza. G˘maza also means to place the right hand first on the left foot. When the right hand is covered next with the left hand, that settles down the mind. In kichij˘za on the other hand, the left foot is placed first on the right thigh (and then the right foot on the left thight) and the left hand is placed on top of the right foot, then the right hand on top of the left hand. That means that we speak of kichij˘za in the case of half lotus as Dogen Zenji describes it - left foot placed on right thigh - while we speak of g˘maza in the case of the full lotus (with right foot placed on left thigh first, then left foot placed on right thigh)."
Although Sawaki Roshi tries to clear up the confusion with these words, I have doubts that he is successful. It seems strange that Dogen Zenji should recommend kichij˘za for half lotus and g˘maza for full lotus. Sawaki Roshi does not tell us why we should sit one way in half lotus and the other way in full lotus. It is interesting but even more confusing that Sawaki also speaks about the hands. In the case of the hands, we should have them in the g˘maza-posture regardless of half or full lotus - according to Dogen read in the way Sawaki does. I am afraid that Sawaki's way of reading Dogen though is not only confusing, but probably wrong altogether.