Lancing the tap hole of a furnace with an oxygen lance.

The furnacemen are burning their way through the clay plug in the tap hole. Molten iron will then flow down the runners made in the sand on the cast house floor. They will direct the flow of the molten iron using gates in the trough (foreground) to iron ladles below the cast house floor.

In earlier times, the iron would run down a large, sand lined trough (the sow) to hundreds of smaller troughs (pigs) where the iron was allowed to cool. When it had solidified, the pigs were broken from the sow and stacked. This is how pig iron got its name.