1. Henry wouldn’t tell his wife what was wrong, but when she asked him if he had lost his job, she could tell by the look on his face that she had hit the nail on the head.
2. We sat around the table trying to figure out why the project wasn’t working. Everyone suggested ideas and possibilities. When Leslie outlined what she thought the problem was, we could all see that she had hit the nail on the head

Synonym: put (one’s) finger on it/(something) , get (something) on the nose.