What Arthur is talking about here is to put a tight string or straight edge from axle to axle. Then measure, perpendicularfrom this line, to the point at whichthe limb meets the riser. The center of the hinge bolt on a Hoyt makes a good point to measure forward to the line. These distances, top vs. bottom, represent the tiller measurement on the bow. For instance, my ProTec is about 7 3/4" at the bottom and 7 3/16" at the top. Hope this makes sense without a picture.