It should be oxtail knife, which evolved from Yanling knife popular in Ming Dynasty. Compared with Yanling Dao, the blade is wider and thinner, lighter in hand and more powerful in chopping. Because there was no chance to face the heavy armor in the late Qing Dynasty, it was very popular. The movie was used by a gossip girl. The single knife of Baguamen has different specifications, and it is heavier and longer than the usual oxtail knife. In the movie, HongLing is wrapped around his hand in order not to be disarmed in actual combat.