Locate center of stud with more confidence and functionality than ever before. The Ryobi Phone Works mobile app and Stud Finder device use your smartphone‚¬TMs technology to transform your phone into a smart stud finder. The stud-scanning device attaches to your phone‚¬TMs audio port and sends an image to your phone screen to let you locate studs behind drywall up to 3/4 in. thick. The free mobile app displays the image and notifies you when center stud is reached within 1/8 in. Simply press the one-handed, no-mess marker on the device to discretely note the spot you need. Enjoy more functional, accurate stud-finding from your smartphone with the Ryobi Phone Works Stud Finder device and mobile app. Store the Stud Finder and other Phone Works tools in the storage case (Sold Separately). Ryobi Phone Works Transform your phone into your smartest tool.