The so-called "double hook calligraphy" refers to writing a certain style of hollow characters directly in a single line. This method originated in the Tang Dynasty. At that time, because there was no printing technology, in order to spread the works of famous calligraphers, people drew hollow characters according to the original works and filled them with black ink, so that viewers could get works similar to the original works. Later, this copying method became a way for people to learn calligraphy, and developed into a splendid calligraphy art treasure in China. "Double hook" is also a calligraphy term. Calligraphy is called "double hook", which is used to draw a stone and hook it out along the outer edges of both sides of its stroke with thin lines.
In the Southern Song Dynasty, Jiang Kui said in "Continued Book": "The double hook method requires that the pen and ink should not faint out of the word, or the outline should be filled in it, or Zhu Qi's back should be fat and thin." Lu Fangweng, a great poet in Song Dynasty, praised the charm of "double hook" with his quatrains of "Mo Miao's double hook post".