Hiking and climbing routes are given a designation of "class" from one to five to describe the difficulty of the route. Always stay within your skill level. Take someone experienced with you if you want to attempt the next class.
Trail and climbs are rated by the most difficult portion of the route. So a class III route may have a section of steep exposed rock without a good trail, but this may be mixed with easier trails.
This is your usual hike on a trail. No special equipment is required and you don't even need any special route-finding skills or devices for class I hikes. There are no obstructions on the trail and no difficulties with significant changes in terrain.
Class two hikes are on more difficult terrain. There may be some places where the trail is not obvious. Walking on snow and walking over uneven talus (large rocks) may be included in this class. Occasional use of the hands for balance can still be considered class II.
Class three hikes can start to be more challenging. The terrain may be steep or more unstable with rocks and so on. Ropes are not required but use of the hands for balance or support is used for part of class III climbs. Trails are not usually obvious and a map and compass and some backcountry skills are required. Exposure or risk of taking a fall causing serious injury or deat occurs on class III terrain.
Class four climbs are just that, climbs. While special rock-climbing gear is not used, a rope is often employed to protect members of the climbing team on a belay or anchor system or to rapel if necessary. Terrain may be unstable and require practice and skill to master.
Class Five is technical rock-climbing and mountaineering. These climbs require protection for most non-elite climbers. Protection is special equipment, such as carabiners and cams used during the climb to anchor ropes to the rock and protect the climbers as much as possible. Practice and training are essential to climbing safety on class V terrain.
A special classification called the Yosemite Decimal System further divides class V terrain from 5.1 to 5.14 to describe the rising difficulties of the route. Letter designations further classify these routes.
select one here...