When I bought this nail finder it was originally intended to be used on my ceiling because the builders who built my house used nails instead of screws to install drywall for my ceiling. Well the nails were starting to show through so I was about to put the screws in. So I bought this device, brought it home and couldn't find anything. So I took it to the rest of the house and started using it on the walls and it found the rivets. Then I figured out which way the joists in the ceiling went, and this is where I was driving the nail finder the wrong way. It worked fine. Make sure it's flush with the wall, hold the button and wait for the beep, then start scanning and slowly move it. I traced it right to left and left to right to make sure I found the center of the beam.