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's technology to transform your phone into a smart stud finder. The stud-scanning device attaches to your phone's audio port and sends an image to your phone screen to let you locate studs behind drywall up to 3/4" thick. The free mobile app displays the image and notifies you when center stud is reached within 1/8". 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. RYOBI Phone Works – Transform your phone into your smartest tool. -- Apple is not endorsing or sponsoring this product. Apple, the Apple logo, iPhone are trademarks of Apple, Inc., registered in the U.S. and other countries. App Store is a service mark of Apple Inc. The Android App on Google Play logo and Google Play are trademarks of Google, Inc.