 into the inside. You've got three quarters of an inch to attach to around the outside perimeter, and now you've got the inside with about three quarters of an inch showing because now that gives you a place to attach this plug to that you're going to stick in there, screw and nail that in, the siding. You could use some caulking on it if you want to minimize some drafting. You can use screws. You can use nails, whatever you want to do.