Boiled leather, often referred to by its French translation, cuir bouilli (French: [kɥiʁ buji]), was a historical material for various uses common in the Middle Ages and Early Modern Period. It was leather that had been treated so that it became tough and rigid, as well as able to hold moulded decoration. It was the usual material for the robust carrying-cases that were made for important pieces of metalwork, instruments such as astrolabes, personal sets of cutlery, books, pens and the like. It was used for some armour, being both much cheaper and much lighter than plate armour, but could not withstand a direct blow from a blade, nor a gunshot.