From Zhang Huai _ "Shu Duan Wang Xizhi". Synonyms of penetration point are: penetrating the back of paper, iron drawing silver hook, etc. The antonyms are: a glimpse of the rainbow, a glimpse of the leopard in the tube, etc.
Book End is a work written by Zhang Huai to comment on calligraphers and calligraphy in the Tang Dynasty. Among Zhang Huai's numerous works of calligraphy theory, Shu Duan has the greatest influence on later generations.
It is divided into three volumes: upper, middle and lower. The first volume describes the characteristics and development of various calligraphy styles; The second volume lists the biographies of calligraphers in the past dynasties in three categories: "God, wonder and ability", and comments on the merits and demerits of calligraphy, which is of high historical value.
According to legend, Wang Xizhi wrote on the board, and when carving, he found that the handwriting penetrated into the board for three minutes. The original description of calligraphy is very pen-like, but now many metaphors are very profound.