1. I see no reason why the human cannot be used to make a Zimun. He certainly is still considered a human and not just a part of a wall.

2. However, there is an interesting and unexpected ramification of this Halachah, applicable on Simchas Torah when everyone is dancing with the Sifrei Torah. The question arises whether one is allowed to sit down during the dancing. It would seem logical that one is not allowed to sit, since one may not sit down when a Sefer Torah is being carried in the room. How, though, can everyone abide by this Halachah, when the dancing sometimes lasts for hours?

3. Rav Shlomo Zalman Auerbach zt'l had a novel idea (cited in Shemiras Shabbos k'Hilchasah, chapter 24, note 118) which he says may be used in cases of difficulty and need. He suggests that the people dancing form a Mechitzah! If the Sefer Torah is inside the circle of the dancers, then there is considered to be a wall surrounding the Sefer Torah. If so, the Sefer Torah is considered to be in a different domain and, therefore, one is allowed to sit down on the other side of the dancers.

4. However, the people dancing must not be aware that they are forming this Mechitzah, as we learn in our Sugya that if the people making up the wall know that they are doing so, the wall is automatically invalidated.

Kol Tuv,

Dovid Bloom