The spectator can look at the cards very closely, but they will never be able to tell whether or how the cards are marked.
This is great for hecklers -- they will try to find marks on the cards but they will not be able to see them.
The cards are easy to mark and can be easily read with the tutorial provided.
Also, I want to give a huge thanks to my family and friend in helping me make this trick.
Download the video and learn this great marking system!