I just put the vice at an angle and clap it down. Usually I can get one stud in the usual place and the other I just use my clamp set for. Put a set square or angle gauge against the fixed jaw and clock that true
If found this image in a good book, although the vice is on it's swivel the scale may not be accurate so I'm clocking it in with an angle gauge and dti, setsquare out of a school geometry set will also do
Edited By JasonB on 03/02/2023 15:53:14