(TopRightLine b3 f3) +++ (BottomRightLine b4 f4) =
    (RightFace b3 b4 f3 f4)
(TopRightLine b3 f3) +++ (BottomRightLine b4 f4) =
    (RightFace b3 b4 f3 f4)
(TopRightLine b3 f3) +++ (BottomRightLine b4 f4) =
    (RightFace b3 b4 f3 f4)