Metal sole protection that you fixed on the heel of your shoes, mostly to make as much noise as possible tap dancing in the school corridor and to make sparks on the pavement as you walked home from school. Did anyone actually ever buy them to protect their shoes?
There were several types that I can recall, the ones I most used were the small half-moon shaped ones that I put on the heels of my shoes. These were supposed to help protect the wear and tear on the shoes and make them last longer, especially important if you are wearing the heavy platform shoes. If you can remember you would put the pointed bits into the base of the shoe by pushing them in as far as they can go. Then you would turn the shoe around and start to use the shoe as a hammer on the floor, forcing the Blakeys into the sole.
Once in you would then walk across the polished floors and tiles, and by doing this you would make a wonderful clipping sound, like a horse pulling a cart on concrete. But when you look back at that very expensive flooring you could see you left a trail of marks and cuts, which was not just taking the polish off, but was also causing considerable damage from all the other Blakey wearers.