I'll tell you how Much I dislike them In starting my tie on nock. When I was removing the Brass Nock I darn near ruined my serving. Never again, plus I know of issues, with crimping the nock too tight and wearing down the string at that point, since it is like a Fulcrum
The not is called a Nail Knot I believe is the Video I watched regarding the nock. Key is to use a Larger diameter serving, I had some great members send me some .30 Halo and it works like a charm.
I got it perfect on my first try... That says something...