1. Expression：lay a finger on

Explanation：To touch someone or something in the slightest way.（轻轻地触碰某人或某物，动某人的一根毫毛）

Example：If you so much as lay a finger on my son again, I'm calling the cops.

如果你再动我儿子一根毫毛，我就叫警察了。

I can't believe the vase shattered like that—I feel like I barely laid a finger on it.

我真不敢相信花瓶会碎成那样，我觉得我几乎没轻轻地碰过它。

The one thing I'll say about my husband is he never laid a finger on the children and he never hit me in front of them.

我要说关于我丈夫的一件事情是：他从来就没有碰过孩子们，也从来没有在他们面前打我。

The girls called out before the head had time to lay a finger on their bedding. （围城）

校长的指甲还没接触到她们的被边时，她们就嚷了起来。

2. Expression：put one’s finger on

Explanation: To identify and state the essence of something. （鉴别……的实质，称述……的实质）

Example: That is correct! You have certainly put your finger on the problem.

这是正确的！你确实指出了这个问题。

Well, I think you put your finger on it when you brought up the issue of tax increases for lower earners.

嗯，我认为你在提出为低收入者增加税收的问题时，已经说到点子上了。

When she mentioned money, she really put her finger on the problem.

她一提到钱的时候，就真的把问题说出来了。

He can't put his finger on what is wrong.

他也说不上问题在哪儿。

Thank you for your putting your finger on my weak spot.

谢谢你正确指出我的弱点。