For this app to work, the nails in your wall should be magnetic and your device (iPad, iPhone or iPod) should have a built-in magnetometer.
To accurately detect nails using this app, on iPhone 5s and below, sweep with the right edge of the device against the wall.
Use your iPhone to find nails in wooden support beams within your wall, or any sort of magnetic metal hidden from view.
Sometimes it helps to first figure out the location of the magnet (compass magnet) on your phone using a magnetic material so it becomes clear where to "mark" when you find a nail in the stud.
DISCLAIMER: The performance of the app is limited by the construction of the wall, presence of a phone cover and/or the material of the nails in the studs.
For iPhone 6 and above, sweep with the top edge of the device along the wall.
Calibrate your device’s magnetic sensor by moving the device in a "Figure 8" pattern.
If your device has a external case, please remove before using this app.
This app does not detect non-magnetic objects, For example, aluminum or wood studs.
Then tap the "Intensity" reading displayed on the app to set the baseline to zero.