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The belt is folded like so
IMG_20180225_004513.jpg

Your job is to put your finger into either of the two holes in the middle.
IMG_20180225_004523.jpg

So when the loop is loosened, it becomes this
IMG_20180225_005336.jpg

Simple right? People still lose. That's the part that baffles me.

Thanks for the pictures. It looks easy to win. Only one hole works?

Yes. You have to pick the right one. It looks easy; I don't know how they make folks lose

This is amazing, i practiced almost every day as a kid to know the secret, yet i know nothing about the trick till date....