"Serving direction", well heres another part to that equasion. Left or right hand shooter! Back a time ago when I was learning to make flemish strings, alot of the adds for custom strings had a request for this. My strings are served with the body twist on my machine, but when I hand served in the beginning I went "both ways". Does it matter? How much rotation are we talking? Josh remember the size or dia. of the material will matter in you measurements. Just as the ratios of gears are determined by the size. Keep it simple and have fun learning, I know I still am! Good shootin, Steve