Looking for a simple iPhone app to do the work of a stud finder? There are a few things to know before you get started. First, no iPhone app can locate 2x4s because phone hardware generally doesn’t include an electromagnetic density sensor to find wooden studs. However, the iPhone’s built-in magnetometer does allow apps to locate metal wall studs, nails, screws or any ferromagnetic material—meaning it also won't work on some types of stainless steel.

ENR compared 16 stud-finding and metal-detection iOS apps. Free or paid, most work the same way—in a more or less user-friendly manner.