I have never tried the bending holes at least that's what I think they are for also.
The threaded bolt I have used a a hold down, I do not know if that is what it is for, but it works good.
Cut a piece of 3/4" or 1" rigid to fit between this bolt and the 'ceiling' (A beam, the metal decking of the above floor etc.) then tighten the bolt, it pushes the vice firmly to the floor. The bolt is off to the side enough to be out of the way.
Most times I do not do this, but occasionally I have and it keeps the vice from tipping when you have 10' of 2" GRC sticking out the back.