(TopFace b2 f2 b3 f3) +++ (TopRightLine b3t f3t) =
    (TopFace b3 f3 b3t f3t)
(TopFace b2 f2 b3 f3) +++ (TopRightLine b3t f3t) =
    (TopFace b3 f3 b3t f3t)
(TopFace b2 f2 b3 f3) +++ (TopRightLine b3t f3t) =
    (TopFace b3 f3 b3t f3t)