There was only one Betto post and was held by the Chunagon (vice-councilor of state), Gon Chunagon (a provisional vice-councilor of state) or the Sangi (counselor) who also held the posts of either Saemon no kami (Captain of the Left Division of Outer Palace Guards) and Uemon no Kami (Captain of the Right Division of Outer Palace Guards) or Sahyoe no Kami (Captain of the Left Division of Middle Palace Guards) or Uhyoe no Kami (Captain of the Right Division of Middle Palace Guards).
定員は1名で、左右衛門督と左右兵衛督のいずれかを兼ねる中納言・権中納言または参議が務めるのが慣例であった。