I have been using a rock for many years and it has worked nicely as long as its done right. I always throw just one rock about the size of a marble a good distance away from the buck or bull, preferrably on the side he isnt facing. That faint sound gets their attention but they normally don't bust. They stare in the direction waiting for movement and when they don't see anything bucks tend to get nervous and stand up for a better view. Bulls can either stand up or go back to sleep which obviously requires a follow up rock. If you throw more than one at a time, they definitely come busting out. Just my two cents.