In Guédelon, the blacksmith's fire is permanently lit. A large leather and wood bellows feeds it using a handle, and all the tools (pliers, rasping hammers, and files) are stored around the hearth. The craftsman heats the tool to be repaired and then works it on the anvil. Once the desired shape has been reached, the metal object is soaked in water or oil to give it the desired hardness. The blacksmith constitutes an essential element for all the other trades in the construction of a castle.