This is the 13158th most frequent Korean word.
두드리자
"두드리자" means "Let's knock."
두드리자 is used here in its imperative form, encouraging an action to be taken.
문을 두드리자.
Let's knock on the door.
두드리자 is used metaphorically here, suggesting taking action to benefit from an opportunity.
기회가 오면 두드리자.
When an opportunity comes, let's seize it.
두드리자 shows a conditional action here, indicating an action that precedes a result.