II Easy to Medium rapids with waves up to 3 feet high, some obvious obstacles to maneuver around. III Medium to Moderately Difficult rapids with high irregular waves, narrow channels, rocks and holes, some maneuvering required. Climbing Ratings Ratings for rock climbing and mountaineering are based on the Yosemite Decimal System. It consists of five general classes, the fifth being subdivided with a decimal notation. Other forms of Climbing such as Aid climbing and Bouldering have there own rating systems that are not covered here, this short explanation of ratings is geared toward educating a first time or begining climber.
Route grading is an art rather than a science.