 If you have a built-in weatherstrip on the bottom of the existing door, usually they're wood doors, you can loosen those screws, and that channel can go up and down a little bit, and you can adjust it that way also. But generally, it's the threshold that needs adjustment. Now, here's the thing. If you're in an older house, if you've had movement in the foundation or the door itself, and you just can't get this done, I like the idea of a storm door.