Until the 1940s protection was provided by the piton, driven into a crack in the rock with a hammer and stoppers. Today, aid climbing uses a considerably larger array of hardware than the pitons used by the first climbers although the primary technique of ascension has not much evolved. The typical gear of an aid climber includes pitons, hooks, copperheads, nuts, camming devices, ascenders, hauling pulleys, aiders, daisy chains, and wall hammers. The invention of camming devices or "friends" and other non-damaging rock gear has resulted in the practice of clean aid, where nothing is hammered, a great bonus for popular routes which could be disfigured from continual hammering.