What is the proper way to anchor a safe to the floor? If the floor is accessible underneath via a basement, couldn't the thieves just break off the bolts or unscrew the nuts? Maybe some Loctite or weld the nuts on?
Well, once again, most people opt for convenience rather than security, like many other things.
A safe in the basement isn't convenient
. After all, you might have to walk down all those stairs, open your safe, get your guns out, walk back upstairs and then do it all over when you're done working (playing) with your favorite weapon.
Secondly, if you DO mount the safe on a floor that is accessible from underneath, you would put the bolthead underneath and the nuts inside the safe. It's much harder to access from beneath, that way. And no, you wouldn't weld them into place.