"If you have a fairly new exterior door with a threshold, you can adjust the height of the threshold to block cold drafts under the door. Simply turn the screws on the threshold to raise it. Adjust until you don't see daylight under the door but not so much that the threshold rubs against the bottom of the door. Installing door sweeps and using draft dodgers can also help to eliminate these types of drafts."
Wilson Ratliff, Technical Director