Challenge 3 in 1 Metal, Voltage, Stud Detector / Tester- I have inherited one of these and need to check our walls before putting up shelves. I've fitted a new battery and tried it on the 3 positions but I'm not sure if i need to be pressing the button in because it keeps buzzing all the time when i do.
Can I use the wall for drilling if there are wall studs in it?
Help please there are no instructions!

what happens if you run it over a metal stud with a cable passin through it????THESE TOOLS ARE CRAP AND SHOULD BE CONSIGNED TO BURN IN HELL WITH THE DEVIL!!!!