Leak mark is a calligraphy term. It is a metaphor for breaking the leak marks between the walls of houses with a pen. Its shape is dignified and natural, hence the name. In the Tang Dynasty, Lu Yu's "shihuaisu and Yan Zhenqing on cursive script" contained: Yan Zhenqing and Huai Su on calligraphy, and Huai Su said: "I think Xia Yun has many strange peaks, and its pleasure is like a bird out of the forest, a snake into the grass, a cliff and a natural road." Yan Zhenqing said, "What's the leak?" Huai Su got up and shook hands and said, "You got it!" In addition, in the Southern Song Dynasty, Jiang Kui's "Continued Book Spectrum" said: "If there are leaks in the family, I want it to be endless."