No more than 1 silkworm head and swallowtail. Only one expressive stroke of silkworm head and swallow tail can be used in an official script character. Too many strokes will look unsightly. The ancients said that silkworms have no two colors, and geese do not fly in pairs. , that is, there should not be two silkworm heads and wild goose tails in one Chinese character calligraphy. The purpose of this is to avoid duplication. The article seems to be displeased with the mountains. Repeated occurrences will affect the beauty of the article, and the same is true for calligraphy creation. As the main character in the official script, the silkworm head that starts the pen and the wild goose tail that ends the pen cannot appear twice in one character. This is one of the important structural rules of the official script.