Originally posted by Kentucky Jeff: With the bowstring as the baseline. You take a line out from the string at a 90 degree angle and where that line sits on the arrow rest is "zero". This is your reference.When you say your nocking point is 5/8" high that means the bottom of your nocking point--brass or tied in. Is 5/8" above the reference point or "zero". That doesn't mean your arrow is 5/8" high. Only the top rear of the nock that sits against the nocking point on the string. The arrow itself may be at a perfect right angle or a slight downward angle to make up for variations in form and tiller.