It is part of the Express Bag Making Process. The first time you load a roll, you will need to make a seal by turning the Lever located on the right side of the Lower Seal and Cut Bar. Once the red light is turned off, you will then be able to Unlock and pull the bag to your desired length. When you are ready to cut the bag turn the Lever back to the Seal function, so that the next use will already have a seal made.