We all know that Craiglist posters can be some of the most trustworthy individuals on this planet, but for those few occasions when you need to double check their honesty there is this great invention: the paint thickness tester. It's a keychain-sized device that can determine if a car has had any body work needing repainting. It works by setting a reference value at a designated spot on the car and then comparing all other spots to that value. For example, you make the reference value a spot on the hood that you're pretty sure hasn't been repainted. Then you go to the common areas for damage like fenders and the bumper to check if the same value exists. The paint thickness tester is available for $20 and could save you thousands. Unless, of course, the paint tester itself is a scam. [Product Page via TRFJ]