put \lay one's finger on 什么意思?

get into the act才是插手
have a finger in the pie是参与其事, 多管闲事, 干涉, 染指

put/lay one's fingers on something 就是正确地指出(位置、问题、症结、病症等)

put/lay one's fingers on something 准确地指出(位置、问题、症结、病症等)