Cut a piece of duct tape, about 9-inches long. Cut the strip in half so you end up with 2 pieces that are each about 9" x 1". Use these two strips to cover and finish the long edges of the wallet. Stick the pieces of tape along the wallet edges as shown and then fold the remaining tape over to stick to the other side of the wallet.
Now there is only one step left to finish the duct tape wallet...