I use a brass nock when tuning and then tie one on when I know exactly where I want it. I have tried the adjustable tie on ones, but they seem to move to much for me, probably the way I tied them. I normally only use one nock, but on short bows, I tie one below as well. The short bows with steep string angle tend to allow the arrow to shift down the string upon my release and the arrow hits the shelf, no matter what I use for brace height. The double nock prevents this. Never had that problem on longer bows which is what I normally shoot.