To prepare for the trick, you need to take the bill of higher value and fold it ahead of time. With the front side facing forward, fold it in half to the left, fold it again in that same direction and then fold it upward. It is important to fold it as perfectly as possible, making sure no corners or edges overlap one another. Once the bill is folded, tape it to the top right-hand corner of the back side of the lower-value bill. Line up the corners exactly as you tape the bills together; you need to make sure no folds of the higher-value bill can be seen peeking out from behind the lower-value bill. You will have an advantage by the way you will hold the bill, but the more perfectly you can conceal the higher-value bill, the better. For best results with the trick, make sure the one part of the higher-value bill that can be seen from the back side is the top right-hand corner.
Hold the lower-value bill out in both hands to your audience, completely unfolded and with the bill's front side showing. If you hold the bill by its top corners, it will help you conceal the folded higher-value bill, which will be in the top corner held by your right hand. Fold the bill in half so that both sides are in your right hand; you are folding it toward the audience's left. Fold it in half one more time in this same direction, so the bill is now folded in quarters. Fold it one last time upward and toward the audience. Every one of these folds has been toward the corner where the higher-value bill is. Now, you only have to quickly flip the bill over in your hands, and the folded higher-value bill will be revealed. As you unfold the higher-value bill, grasp your index fingers within the last (upper) fold of the higher-value bill while holding the lower-value bill folded in place with your thumbs. The quicker you can learn to do this, the easier it is to pull off the trick.