This diagram enables the user to craft hardened leather. It can be purchased from one of the following merchants: * Fioravanti in Flotsam * Mysterious merchant in Flotsam's harbour * Sambor in the camp followers' encampment * Felicia Cori in Vergen's Rhundurin Square (Chapter II, Iorveth's path) and in Loc Muinne (Chapter III) * The Incredible Lockhart in Loc Muinne