Bolts to frame. I don't know if any drilling is required. I never even got that far with it. It has been moved around my garage since the day I got it.
I'd buy it but I have something like it already. I use mine as a winch mount, foot step, bumperguard, 'no scratch' towhook/chain spot and other stuff. It's nice to have and it doesn't add weight like a 500 lb bumper.