The "blade" of a cricket bat is a wooden block that is generally flat on the striking face and with a ridge on the reverse (back) which concentrates wood in the middle where the ball is generally hit. The bat is traditionally made from willow wood, specifically from a variety of white willow called cricket bat willow ("Salix alba" var. "caerulea"), treated with raw (unboiled) linseed oil, which has a protective function. This variety of willow is used as it is very tough and shock-resistant, not being significantly dented nor splintering on the impact of a cricket ball at high speed, while also being light in weight. The face of the bat is often covered with a protective film by the user. In 1900 Percy Stuart Surridge developed a reinforced toe.