Sealing and maintaining a proper door threshold provides many benefits for today’s homeowner. Sealing and maintaining a proper door threshold provides many benefits for today’s homeowner. Aluminum Thresholds A door threshold can really be sealed in one of two ways. With an aluminum threshold, which is often common with entry doors instead of garage doors, the aluminum is spring loaded to form a tight seal with the door when it is closed. The door slides easy over it when opening and closing, but the tension of the spring physically pushes the seal closed in order to seal out the air. Rubber Thresholds A more common solution is a rubber door threshold because it forms a tighter seal than most aluminum or spring loaded thresholds.