Dibona, on the other hand, was an advocate of security and was not fundamentally averse to pitons. When Luis Trenker asked how many pitons he had hit in total in life, Dibona replied: "Fifteen, six of them on the Laliderer north face, three on the Ödstein, two on the Croz dell 'Altissimo, one on the Einser and the rest on other difficult climbs." Aid climbing, climbing using equipment that acts as artificial handhold or footholds, became popular during the period 1920–1960, leading to ascents in the Alps and in Yosemite Valley that were considered impossible without such means. However, climbing techniques, equipment and ethical considerations have evolved steadily. Today, free climbing, climbing using holds made entirely of natural rock while using gear solely for protection and not for upward movement, is the most popular form of the sport. Free climbing has since been divided into several sub-styles of climbing dependent on belay configuration. Over time, grading systems have also been created in order to compare more accurately the relative difficulties of the rock climbs. On August 3, 2016, the International Olympic Committee (IOC) formally announced that sport climbing would be a medal sport in the 2020 Summer Olympics. The event debut was postponed to 2021, due to COVID-19. Style In How to Rock Climb, John Long writes that for moderately skilled climbers simply getting to the top of a route is not enough- how one gets to the top matters. Within free climbing, there are several distinctions given to ascents: On-sighting a route requires that the climber ascend cleanly (without any falls or rest with the assistance of artificial equipment) on their first attempt without any foreknowledge. Flashing also requires a clean ascent on the first try, though the climber has previous information about the route (often called beta). This may include talking about the with other climbers about the route or observing others climb the route. Redpointing means to make a successful free ascent of the route after having previously tried it. This may include multiple days or even years of "working" the route to learn the specific sequence required. Pinkpointing means to make a successful free ascent of the route after having previously tried it, with protection (or "pro") such as quickdraws or trad equipment pre-placed on the route. Style is mostly up to each individual climber and even among climbers the verbiage and definitions can differ. Climbers