Indoor Climbs IL: Warrenville Vertical Endeavors     built with Nicros Art Walls TX: Dallas Stone Works Climbing Gym Yosemite Decimal System info from rec.climbing Class 1 Walking on a trail Class 2 Scrambling with use of hands Class 3 Steeper climbing with handholds, some exposure, usually no need for a rope. Class 4 Steep, exposed, but easy climbing with rope for safety. Class 5 Technical rock climbing - specific climbing moves necessary, with a rope and intermediate protection necessary on each pitch. Originally this was split up from 5.0 - 5.9 but, as time went on people did harder climbs, hence the present state of the art, 5.14. Class 6 This is how aid climbing was originally denoted. This has since been shed for the current aid rating systems, which are denoted by A0 - A5, based on difficulty of the aid placements, and the danger of a prospective fall. more info HERE