Mounting shelves to drywall. Anchors are easy to set into the wall and aren't too difficult to install, but this is where the problems start. Inserting them into the wall and then pulling on the head of the screw to unroll the wall anchor will drive the anchor into the wall, but it will also strip the anchor's threads. As a result, you have a tightly embedded drywall anchor that prevents the screw from tightening. The screw just spins in the hole and it does the same thing even though I increased the size of the screw. This has happened to 2 of the 4 Mollys I have installed so far. I very rarely, if ever, leave bad reviews, but this only made installing my shelf more difficult as I can't get the anchor out without significantly damaging the drywall.