臼杵之交

Explanation: Acetabulum: stone of Tsuishine apparatus. Pestle: Tsuishine the stick. Incompatible with the pestle from the mortar. Analogy is very good friends. 　　Source: "East View Han Ji Wu Yu Chuan" public Shamu autumn outing Imperial College, no MERITS, is changing clothes off commission for the woo with Chung. Yu and language, shocked. Then were fixed between the cross on the ball and socket. " 　　Examples: Wendeng week students, and adult students were less Bi Yan then as ~. (Qing Pu "Strange immortality")