This will act as a retainer to keep the nut together...…..after you cut the nut in half to get two "C" shaped pieces. This is effectively a 2 piece collet that will grip the threads without damage and will also keep the bolt from spinning.
I have also had good results from just cutting down one side of a nut, the cut will spring enough to grip in a vise or chuck. If for whatever reason you need a "softer" collet, you can continue cutting part way through on the other side (I like to cut the last side from the threads side) while still leaving it in one piece.
