Really great.

a meaningful work. Even in Korea is very common as an expression. I can say that Koreans are very smart in giving instructions and advice. not necessarily with words, but with symbols that for others can be very difficult to understand.
Only people who have "finished" with their life can understand a symbol. And the great thing is that this work is just an ordinary roof, but with high scrutiny you can decipher it well.
Thank you @slowwalker
Warm regard from Indonesia