In my work, I often have to fix things in computer code. Every now and then, I will spend a long amount of time trying to fix something without success only to suddenly remember that I had handled the exact same problem before and that there was an easy way to fix it that I had forgotten about. That moment is a perfect moment to say "Of course, DUH".

It kind of means that you are incredulous about how long it took you realize something. You can use it to make fun of another person who is having trouble "finding a clue" as we say, but it is more often used to make fun of yourself.

It's an idiot This is a stupid question ((Which, by the way, it is not))

When do you Americans use the word "Duh" and what does the word actually means to?
Can I ask for an example of a situation for where you'd say "Duh"? lol