My first ever climbing or ropework excursion involved rappelling off of the side of a 4-story building. Needless to say it was terrifying, especially since our ropes had to go around a sharp 90º steel edge with no more protection than a layer of cardboard. Convinced that this was an issue I would face often as a rock climber, I made this aluminum rope guide/protector for allowing ropes to go smoothly over sharp edges without damage. Ironically I've only used this about twice in the 3 years since it was made. But it did work as planned. The material is aluminum.