不落痕迹bù luò hén jī

leave no traces
❍ 潘信诚从来不先表示态度的，提人选的事他更不干，要等待大家提出符合他心意的人选，那时候他才点头，这样～，也有把握。(周而复《上海的早晨》Ⅰ—435) Pan Xincheng always preferred not to state his own attitude before other people had spoken,and he was even less willing to do so in this matter of suggesting candidates; he would not give his nod of assent until the others had suggested a name that was agreeable to him; that way was safer and left no tell-tale traces of the hand he had in it.