knock an arrow (make sure it will be long enough for that bow), have your friend or you pull back full draw and mark the front of the arrow just above the grove in the hand grip. Than add 1 3/4" and that isthe bows draw lenth. Or to make it simple, most bows risersare @ 1 3/4" deep, so you can get pretty close to marking the arrow at the front edge of the riser. Than measure the arrow from the middle of the nock ( where the string seats) to the mark on the arrow.