Ah, the lowly Parrot Vise. Often under-appreciated except by gunsmith's and maybe carvers. I bolted mine to a carriage that clamps in my bench vise:
I shaped some swivel jaws out of some scrap maple leftover from some from some old commercial furniture. I added a small magnet in each that makes the jaw open and close with the vise yet still allows them to pivot when required:
It works great for holding small odd-shaped parts like a "pull" idea that I am playing with for a box . . . the scale isn't quite right yet . . .
The carriage is long so I can have some clearance if I really need to hang things out there.
I just wanted to share since it is proving very useful for something I am playing with right now. You never know, this thread might help someone out there who is having a difficult "holding" problem.