Notes on climbing at Cannon are here . He did not even protect the belays, instead using a comfortable and secure stance. On some climbs, especially on climbs in the Swiss Alps, he did use pitons for protection. His piton hammer and pitons are shown. Aid climbing developed into its own style, still practiced today.
More rock climbers practice free climbing than aid climbing.
Clean climbing became popular in the 1970's in free climbing circles. Clean protection is gear that is easily placed and removed from the rock without harming the rock. Pitons damage the rock because they are driven in and pulled out with a hammer. The idea is to do the hardest climbs possible in relative safety. Sport climbs usually rely on bolts for protection.