In the Water Margin
Jin Dajian is the sixty-sixth hero of Liangshan, born under the star Diqiao (地巧星). He lives in Jizhou and is the finest engraver of his day: he carves seals in jade and stone, and cuts the inscriptions on memorial tablets. His nickname, Jade Seal Carver (玉臂匠), means literally the craftsman with arms of jade.
He is pulled into the story by Song Jiang's arrest in Jiangzhou for writing rebellious verse on a tavern wall. The local prefect, Cai Jiu, sends the courier Dai Zong to his father, Grand Tutor Cai Jing, to ask what to do with the prisoner. Dai Zong stops at Liangshan, and Wu Yong decides to answer the letter himself: a forged reply in Cai Jing's hand ordering Song Jiang sent to the capital, where he can be rescued on the road. The calligrapher Xiao Rang writes it; Jin Dajian cuts the seal. At Liangshan he goes on making the band's tallies, seals and documents. After the amnesty the court keeps him in the capital, in the palace office that makes the imperial seals.
Key episodes
The commission at Mount Tai. To bring the two craftsmen to Liangshan, Dai Zong poses as a temple official from Mount Tai and offers them silver to write and carve a new stone tablet. On the road, a band of outlaws carries them off to the mountain.
The forged seal. Jin Dajian copies Cai Jing's seal so well that no one could tell it from the real one. Dai Zong sets off with the letter, and only then does Wu Yong cry out: it is Cai Jing's personal name seal, which no father would use on a letter to his own son.
Saved at the execution ground. In Jiangzhou the scholar Huang Wenbing spots the same flaw. Dai Zong is arrested and condemned beside Song Jiang, and Liangshan has to storm the execution ground to save them both.
