Wizard Detectors 23800 Wall Wizard Stud Finder Metal detector / stud finder / AC-DC tester Precisely locates studs by detecting the screws which hold the drywall onto the studs AC electrical current can quickly be detected from 12 to 600 VAC DC voltage over 9 volts can easily be indicated by simply holding the tip of the Wall Wizard to the positive post on a battery while grounding the negative post with your finger Perfect for checking polarity