How to do this magic:
Firstly, prepare a piece of paper, then divide it into nine parts. Give one piece to the audience and let him/her make a mark on the pieces. And put these pieces into the other eight pieces and choose the one that he/she marked. The important point is how to divide the paper. First, divide the right 1/3, then put it in the middle Then divide the left 1/3 and put it on the top of the left part. The divide the right1/3 and put it on number 4 piece, and divide left 1/3 on the top of piece 7. Then you can find out that number 5 is at the bottom. Then put number 5 on the top. This is the piece that the audience marked. This is the only one that all the edges are coarse.
This magic uses a little trick of the little differences in those pieces. Just one of those pieces is totally different than others. And these slight difference cannot notice. So this magic is very easy to apply. Just use a little bit of skill to divide the magic.