I have had one of these for years and been meaning to post about it except its never here as mates keep borrowing it!http://img.tapatalk.com/d/14/05/31/4uvebuqe.jpg
It swivels the knife 180 by just pulling the the clamp out and turning.
A 2 second job compared to unbolting and flipping over.
I had to borrow it back as all my knives need dealing to!