Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Never gave same reading twice

My wife bought this piece of junk, so if I wanted to keep getting fed, I had to try to use it to put up the shelves she wanted.Running it over wallboard was useless, since it never located the same stud twice. On one pass it beeped for a stud & on the next pass the stud had suddenly disappeared. The only thing consistant with this stud finder was its inconsistency in finding studs.Luckily, it soon fell out of my pocket into a bucket of paint, which solved my problem. Now I have better luck finding studs by tapping the wallboard & driving in a thin nail where it sounds solid. Actually, my problems are not completely solved, since I still have to put up the shelves.