Have several stud finders - A Stanley and a Zircon, occasionally they make a mistake, both mostly right on. This Black and Decker gets it right 1 out of 100. Yes, it was cheap, but so were the others. I need several - one in each truck, one home, one tool box-because of what I do. Don't need anything fancy, but this is a joke. I have figured out how to use it though-go to the left four times and mark the beep (each one will be different). Go to right 4 times, mark as above. Find center between two outermost marks and two inner most marks. Mark each on, and measure differnce between, add difference divide by 2. mark that spot. Drive in nail. if you don't find a stud, drive nail again 1/8 inch to left. Keep driving nail at 1/8 intervals until you find a stud. This is stud edge. Meassure 3/4 in to left. This is center. Mark center. Patch holes with drywall compound.
It think they have discontinued this item. Good riddance.