Mid 1920's
"Metal edges on wooden skis had been introduced in the mid-1920s, allowing skiers to edge more effectively. However, these edges were screwed into the wooden body of the ski and often came loose and could break. This resulted in many skiers carrying spare edges and tools to make field repairs, which was not ideal."
"1926: Austrian accountant and skier Rudolf Lettner developed the first ski with metal edges after a slide-for-life incident nearly killed him. It took him a decade to figure out how to attach the metal edges to wooden skis. “Metal edges held better on hard snow and ice, and they made skis stiffer and less likely to break,” says Lowell Skoog, a Washington ski historian and co-founder of the Washington State Ski and Snowboard Museum. “All of these factors led to greater control at higher speeds.”