Saucers for sliding downhill during the winter. At first they were metal... later on plastic. (Where I lived as a child there was a hill we slid downhill on, on saucers. The "course", so to speak, ran down one hill, across a street that was closed during the winter, between 2 concrete posts & then down a second hill. One day when we showed up there to slide, there was blood in the snow by one of the pillars. Another kid said someone had tried to slide down the course on a toboggan.)