Review on Stud Finder Wall Scanner - 4 in 1 Electric Wood Detector: LCD Display, Center Finding & Sound Warning – Black by John Koch

With this device it points to studs where there are none. This led me to believe that the room I was scanning in had fire protection. I actually found blueprints for this room that also showed where the rivets should be. There is no stop fire. It's also frustrating when you scan once and think you've found a hairpin, but you scan again and suddenly it's gone, or suddenly there's an extra hairpin, or there really should be 2 hairpins right next to each other, otherwise it is a really wide hairpin. Multiple scans only add to the confusion. After I decided, "Anyway, I'm pretty sure there's a hairpin here," and drilled through the wall, it became clear that I hadn't hit the hairpin. Don't waste your money on confusion and frustration. You might as well hang a magnet on a string to find where they nailed the drywall to the studs.