Door bottoms, sometimes referred to as door sweeps, are a cheap and practical solution to improve your home's resistance to drafts. Door sweeps and bottoms are fitted to the bottom of your door to act as a physical barrier (usually made of rubber) to keep out cold air that may otherwise leak through the gap between the floor and door bottom. An effective means of repelling rats and insects.Door bottoms, also known as door sweeps, are a cheap and practical solution to improve your home's resistance to drafts.