Thats a question that I really can't answer without seeing a picture of what you are talking about. Stuffit is designed fill small holes and cracks. If you have an area behind a shutter, it will take a lot of stuffit, which will work. It really depends on how large the gap is. If nothing else, just fill the void where they can't get in. Fold it, bend it or however it works best. That's why they call it Stuffit.