TV series example of the word

The Big Bang Theory Season 5, Episode 1
(knock on door)

Breaking Bad Season 3, Episode 12
Knock, knock.

The Big Bang Theory Season 8, Episode 21
Now, why don't you boys step aside? Let me knock this project out.

The Big Bang Theory Season 12, Episode 9
Come on, knock on the door. You can do this.

The Big Bang Theory Season 4, Episode 9
<font color="#808080">BERNADETTE</font>: Knock, knock.