I don’t know who invented these awful contraptions, but they were lethal! They sort of expanded in the middle to fit your foot by adjusting the screw. You wore your sneakers & they strapped over the top. When you lifted your foot, the skate had a slight ‘dangle’ & it clunked on the pavement with every step. I remember they NEVER went in a straight line & you took your life in your hands every time you put them on!