Adjusting draw weight to perfectly match the bow to the arrow's spine. It's part of what's called 'tuning the bow to the arrow,' Roskoe.It goes hand in hand with adjusting the bow's tiller toperfectly match yourgrip. I've tried to get this across for years now.People who crank the limb bolts all the way down and leave 'em there are ignoring the single greatest benefit of having a bow with adjustable draw weight.