I used 6 or more. Of these 6, three broke off at the base when tightened. I mean the flared part where it joins the flat part with sharp, raised edges. the in the drywall goes so it doesn't turn when tightened.I used a regular screwdriver and hand tightened it and no I didn't over tighten it.After the first one broke I could hear I went on the next one, which I installed, very slowly and carefully, until I felt a slight firm resistance, but it broke anyway.