I agree with the previous repondents. I used to try to tune individual bows to optimize nock height, but always seeemed to end up with the same measurement (5/8ths inch in my case). I tend to think it's more a factor of your release (split vs. 3-under), anchor, form, etc. Not that some bow's tiller may affect it and your mileage may vary. I also found that there's a technique variable that comes into play when you prefer a rest material with "give", like the sealskin that I use. In other words, if you get a bit sloppy with the downward pressure on the square when you clip it to the string, your measurement can vary. The bow squares that have a rounded rod don't seem to be as prone to this, but I prefer the precise markings on the Potowatomi type. It has a thin aluminum blade, but I split a section of old aluminum shaft and attached it where the square lays across the rest to make attachment more "repeatable". Then I marked my desired nock height on the scale with a Sharpie.