The Yosemite Decimal System
- Class 1
- Class 2
- Simple scrambling, with possible occational use of the hands.
- Class 3
- Scrambling; a rope might be carried.
- Class 4
- Simple climbing, often with exposure. A rope is often used. A fall on Class 4 rock could be fatal. Typically, natural protection can be easily found.
- Class 5
- Where rock climbing begins in earnest. Climbing involves the use of a rope, belaying, and protection (natural or artificial) to protect the leader from a fall.