The factory had some kind of nutcert for the mirrors, but when I went to take them off, they just spun and spun. I had to go from the inside to hold them in order to unscrew the mirror. When it was time to re-install them, I took 1" flat bar, 1/8" thick and 7" long, drilled and tapped them for the screws, and epoxied them in place inside the door. They'll never spin again and I won't have to go into the door to hold anything. Plus it spreads the load across the whole length of the mirror.