Hi, my name is Steve Nichipor, I'm a professional mountain guide with Bretton Woods Ski Area, and I'm going to show you how highest difficulty level for rock climbing. The most commonly used method for rating the difficulty of rock climbs is called the Yosemite decimal system. The five designates any fifth class climb where a rope is generally needed for security. The second number, originally meant to go from zero through ten, designates the difficulty within that range. Now, climbs go all the way up through five-fifteen where the climbers have pushed the difficulty even harder. During the 1970's, climbs rated five-nine got harder and harder, then climbers began to push into the five-ten range. After this point, as climbers were able to climb harder and harder roots, the scale was expanded into five-eleven and above. Today the hardest climbs are rated five-fifteen, which is only possible for a handful of the world's best climbers. Beyond five-ten climbs are often rated with a sub grade of an A through D, with A being slightly harder than the number grade below and the D being almost as hard as the next higher number. For instance, a five-ten A would be slightly harder than the hardest five-nine, and a five-ten D would be almost as hard as a five-eleven. However, these ratings are very subjective, and two climbers may have very different perception of difficulty on a given route. Generally, beginner roots are grades five-zero through five-five, intermediate roots from about five-six to five-eight, expert routes from five-nine to five-eleven, and elite roots from five-twelve and up.