Bouldering is a form of rock climbing that is performed on small rock formations or artificial rock walls, known as boulders, without the use of ropes or harnesses. While it can be done without any equipment, most climbers use climbing shoes to help secure footholds, chalk to keep their hands dry and provide a firmer grip, and bouldering mats to prevent injuries from falls. Unlike free solo climbing, which is also performed without ropes, bouldering problems are usually less than 6 meters tall. Traverses, which are a form of boulder problem, require the climber to climb horizontally from one end to another. Artificial climbing walls allow boulderers to train indoors in areas without natural boulders. In addition, Bouldering competitions take place in both indoor and outdoor settings.