Where the arrow rests. That's how you figure the nocking point in relation to the rest. That being said, it really doesn't matter whether it is square or not. You still have to shoot the bow and tune it to where your arrows fly the best. My present bow just happens to like the nocking point 1/2" above square. That where abare shaft goes the best out to 25 yards. I'm still tweaking and trying to get it to 35 yards, but I'll get it.