Often confused with "free climbing", solo climbing (or free solo climbing, or simply soloing) is the practice of climbing without ropes, harnesses, mats or any other form of protection. At very low heights this could be called bouldering, but solo climbers have been known to climb some immense routes, hundreds of metres above the ground, with barely a pair of rock shoes for company. Failure is simply not an option. Alex Honnold is one of the leading figures in solo climbing, and climbs some unbelievable things. Makes my palms sweat just thinking about it.