What does "hit the nail on the head" mean?
It means that a person said exactly the right thing to either define what the problem is (for example, in a business or in a relationship) or to identify a solution.
1. I'm glad you said that: you hit the nail on the head.
2. You are right: you hit the nail on the head.
3. We were talking about what the problem might be, and he hit the nail on the head.