In order to make a non-overlapping jib as big as possible, it needs battens. Without battens, the leech of the jib would need a concave profile to keep the back edge of the sail from curling. By adding battens, the leech of the sail can be straight from the head to the clew, or even with some positive roach. In order for the battens to roll up with the sail, they are positioned parallel to the luff. The only draw back to vertical battens is that they need to be more than twice the length of horizontal battens in order to support the leech. Longer battens add weight and they are not easy to insert.