Metal rails, upon which balls would be deposited: Firebox, in which fire would be kept a-burnin' hot; Ash pit, which is, y'know, a pit into which ashes fall. On the wall to the left is a sign assuring us that this is, in fact, a hot shot furnace...or maybe a "hot shot oven," as the sign manages to refer to to it both ways. Click here to see the slightly confused sign.