Knubel was taught to ski by Arnold Lunn and later began to use skis while traversing mountain ranges. In February 1920, Knubel and Marcel Kurz, using skis, made the first winter ascents of the Wellenkuppe, Ober Gabelhorn, Schallihorn, and Täschhorn. He became an authorised ski-guide in 1925. Throughout his career, he made over 800 ascents of Alpine peaks higher than (four-thousanders) and led around 120 clients.