So far, I have scraped the old undercoating out of 3 wheel wells. Not a pleasant job if you are 6'3" and have a bad back. I made scapers out of 1/8" plexiglass and put a bevel on the end. Don't use the bullet-proof stuff, too soft. Plexiglass is much harder, but will not cut through good paint-they'll hold an edge a long time.