Those good ol' fashioned metal roller skates that strapped onto your shoes were useless if you didn't have a skate key on hand to adjust them. The hexagonal loop on top was used to turn the bolt that adjusted the length of the skate and the tubular end fit on the pin that tightened the toe grips. The long narrow hole in the middle? Why, that was for stringing a shoelace through so you could wear the key around your neck while skating.