空白纸

plain washer

flat key (parallel key, plain key)

plain steel

Plain Questions 70, Great Treatise on the Five Normal Rules

Plain Questions 74, Great Treatise on the Essentials of Supreme Truth

Plain Questions 30, Treatise on Heat

Plain Questions 10, Treatise on the Engenderment of the Five Viscera

Plain Questions 33, Treatise Discussing Heat Disease