Repair carpet holes, burns or small permanent stains by cutting the spot out with a razor blade or scissors. Replace with a piece you've cut from a hidden place, such as underneath the seat. Use a water-resistant adhesive to keep it down. Always ask the owner of the car for permission before doing this step. If you want, have a sample repair that you can show the owner of the car of what the process will look like. If it's done well, this sample will be reassuring.