It can work on cheap wall and also depending on what kind of cup your using. Shades
I use a glass cup, and I did it on the door. Thatโs pretty much it when I try to find my birthday present. Wondering why would my family lock themselves in a room to wrap a present on the same day without doing it some other days before. That made no sense, now, as an adult. (โ๏ฟฃ(๏ฝด)๏ฟฃโ)
HE PUT THE CUP TO THE DOOR