投刃皆虚

Explanation: "Zhuangzi health master" that Paodingjieniu, after three years have seen none of the whole cow, saw its joints are empty, "he who has leisure section, and the blade had no thick, thick into a no-idle, then the long arm of there must be room to carry on its brief statement. " Later, because of "cast are virtual blade" metaphor processing services handy. 　　Source: "Zhuangzi health master" that Paodingjieniu, after three years have seen none of the whole cow, saw its joints are empty, he who has leisure section, the blade had no thick, thick into a no-idle, then the long arm of there must be room for maneuver carry on. "