It can be nearly impossible for an untrained eye to know if they’re getting a safe and reliable car when shopping at a dealership or from a private seller. Bringing a magnet when buying a used car can give shoppers one quick way to spot signs of previous body repair.

Cosmetic repairs can make a used car look better than its condition suggests. A fresh coat of paint can make an older vehicle look surprisingly clean. There’s one simple trick shoppers should be aware of to help check for signs of previous repair work: bring a magnet .

The test takes only a few minutes, but it works best when shoppers understand its limits.…