锋芒不露

Explanation: Edge: the tip of the sword, metaphor skill or brains exposed; exposed: exposed. Talented or not exposed brains. Described as full of talent or effort, on the surface does not come out. 　　Source: Song Shen, including "Meng Xi Bi Tan fill": "Song Kou Zhun worship phase, the court that under the edict are: 'to break big, sloppy; are go-getters of the device, do not reveal edge, pregnant according to the specified object, and can accommodate. "