This is the most delicate step in the process. Carefully fold all the score marks in the proper directions: all the ridge folds out and all the valley folds in. You will need to work your way into this, creating partial folds first, and then returning to create sharper and sharper folds. A small steel rule can be helpful during this process. As you progress, you can begin to fold the card in half. When you are finished, the card should easily open and close without obstruction.