Rats and mice are lazy enough to use the doors we provide. The openings at the bottom of the door are the first areas to seal to the outside. Replace or add a door sweep to the side of the door with the door stops (the inside of the jamb) so that air cannot easily leave with heat, or in the summer cool air, and the accompanying smells to the outside. A brush style sweep is the most efficient at dealing with different surfaces. These photos illustrate vinyl door sweeps chewed open by rodents.
Inspect your doors today. Replace missing and damaged sweeps. Door sweeps can be installed on either side of the door. Install high-quality brush style sweeps flush to the floor on the doorstop side of the door. To clarify, the doorstop is the part on the door frame a closed-door is shut against. Make sure the sweep holder sits above the bottom of the door so the door can open and close freely.
The openings needed by mice and rats are small. Mice need just a 1/4 inch opening or a hole the size of a dime and rats need a hole the size of a quarter. Insects need an opening as small as 1/64th of an inch. That is the size of a piece of paper. Push down on the sweep holder when replacing or installing sweeps to make sure of a tight fit to the threshold. The threshold will wear from traffic over time into a slightly concave shape. This allows air to escape. Rodents smell the escaping air and chew around the flow to expand the opening.