It's just a wooden door. I don't think the door is sagging, but if I take the metal plate off the floor and the rubber weatherstripping off the bottom of the door then there is a gap between the door and the floor. I'll try and remember to take a picture tonight, I totally forgot to do it yesterday.
What I have there now looks like this:
Tago | Vin For Met Door U Bottom Br | Home Depot Canada
I'm just wondering if there is something better I can put that will seal it better.