Start by folding the white border (no more , no less) at the top and bottom of the bill toward the front side . The picture here only shows the end , but do this evenly down the entire length of the note .
Fold the bill precisely in half lengthwise , twice . If you've folded very carefully , the 'one' insignia will be evenly framed top and bottom , and the width will be even along the entire length .
On one end , fold the white border at the edge back . Fold on the other side of the 'one' insignia so that it is evenly framed in a square as shown .
To simplify the description in the following steps we'll call this end of the bill the *head* . The other end of the bill will be called the *tail* .
Start curving the bill away from the head as shown . Pay attention to the direction of the curve relative the folds made in the head . If you curve the wrong way you won't be able to complete later steps . It sometimes helps to 'rub' over the corner of a tabletop or similar surface to get a nice curve out of a stiff bill .
Next , make a 90 degree bend in the bill as shown . Where this bend is made will determine the size of the ring . The further from the head, the larger the ring .
Now wrap the tail tightly around as shown . In this picture the portion to the left is shown in the same position as in the previous picture , and the tail folds underneath .
Using the curve created three steps above , loop the head back around to a position on top of the 90 degree bend made in the previous steps . Continue wrapping the tail around the body of the ring until all the excess length of the tail is used up . If you've followed the previous steps closely , the very end of the tail will be on the outside of the ring (under the bend in the head) .
This picture shows the tail wrapped all the way around and the head at the top of the photo . Using your fingernail (or anything else convenient) , spread the gap between the wrapped portion of the tail and the body of the ring . In this gap , tuck the last fold in the head .
This photo shows the finished product .
This also works well with 10s and 50s . 5 and 20 dollar bills work , but require a bit of adaptation due to the difference in size and position of the denomination insignia in the corner of the bill .