Deer Horn Knives, also known as crescent moon knives or duck blades, are specialised Chinese bladed weapons consisting of two steel crescents crossing. They are used in Chinese martial arts. This crossing produces four curved, clawlike points, one of which is extended as the “main” blade. The practitioner grips the wrapped middle of the lengthened crescent with the other acting as a hand guard. Relatively short weapons that were easily concealable in traditional Chinese clothing, they are usually trained in pairs, one for each hand, hence the plural title of the article. (source)