隔行如隔山 [ㄍㄜˊ ㄏㄤˊ ㄖㄨˊ ㄍㄜˊ ㄕㄢ; ge2 hang2 ru2 ge2 shan1] different trades, worlds apart (idiom); to sb outside the profession, it is a closed book ◄ ►