Fill small holes with steel wool. Put caulk around the steel wool to keep it in place. Use lath screen or lath metal, cement, hardware cloth, or metal sheeting to fix large holes. These materials can be found at your local hardware store.
What do you do with a rat hole?
You can use wire mesh or even chicken wire to block the holes and this will prevent the rats from re-entering the hole. If you do not wish to kill the rodents, be sure to flush the rat burrow first and then proceed to block the rat burrow once you are sure there are no rats inside.
What do you pour in rat holes?
Fill in the burrow with soil or dirt. If possible, place some used cat litter in the hole before sealing it. Cat urine will cause most rats to leave. Cover the cat litter with dirt, and pack it down so the soil is secure.