quick question, stuck on front brake job

I am helping a buddy do rotors and pads all around on his 2000 GT.

Currently doing the fronts:

I have the old rotors and pads off, new rotors installed, caliper braket installed and have the caliper back on with the new pads.

My question is how the heck do you tighten the small caliper bolts? (12mm i think) They go on so far and then just spin...and on the inside there is a round portion that is spinning that they bolt into, it's not like a nut that I can put a wrench on though.

Do you just grab that part with a vice grip and chew it all up to get it to stay still? They don't seem nearly tight enough, there is still too much play in them.

Any ideas?

thanks

Thanks, it was pretty dirty so I definately did not notice those, I will try to scrub it up a little better and go with the adjustable wrench like you said.

A big thanks for the reply!