  Passing Oneself Off as a Member of the Orchestra 滥竽充数

  In the Warring States Period, King Xuan of the State of Qi loved to listen to the yu -- an ancient wind instrument. He would order 300 musicians at a time to play the yu for him. Mr Nan Guo, who couldn't play the instrument, passed himself off as one of the musicians. When King Xuan died, his son King Min succeeded to the throne. King Min also loved yu, but he preferred solo performances. Mr Nan Guo thereupon slipped away from the orchestra. 
  战国时代，齐宣王非常喜欢听吹竽，而且每次总要三百人同时吹。有一个南郭先生，本来不会吹竽，也混在中间凑数。后来，齐宣王死了，他的儿子齐湣王继位。湣王不喜欢听很多人同时吹竽，而要听一个人一个人地吹。南郭先生知道自己没办法再混下去了，就偷偷地溜走了。

  This idiom is used to describe those who have no actual skills but pretend to be experts, or the passing off of inferior things as high quality ones.
  "滥竽充数"这个成语比喻没有本领而冒充有本领，或者拿次货冒充好货。