ㄏㄢˋㄋㄧㄡˊㄔㄨㄥㄉㄨㄥˋhànniú‑chōngdòng

汗牛充栋
  1. 牛車出汗屋子一直屋頂形容書籍 老先生藏書可謂汗牛充棟」。

lit. enough books to make a pack-ox sweat or to fill a house to the rafters (idiom)​; fig. many books