That when we were little and could'nt afford one of those fancy store bought sand boxes. So instead dad went out to the neighbors farm and got own of their old tractor tires no longer any good for work brought it home sat it in the yard and filled it with that sand with the little pebbles in it?Mine definatly did I look back on it now and laugh. It makes sense I guess it was free and it was big but i was the only kid I knew and still know who ever owned one. Lol memories.