A throwing knife is a knife that is specially designed and weighted so that it can be thrown effectively. They are a distinct category from ordinary knives. Throwing knives are used by many cultures around the world, and as such different tactics for throwing them have been developed, as have different shapes and forms of throwing knife. Throwing knives are also used in sport. Central Africa Throwing knives saw use in central Africa. The wide area they were used over means that they were referred to by a number of names such as Onzil, Kulbeda, Mambele, Pinga, and Trombash. These weapons had multiple iron blades and were used for warfare and hunting. A maximum effective range of about 50 yards has been suggested. The weapon appears to have originated in central Sudan somewhere around 1000 AD from where it spread south. It has however been suggested that the same weapon is depicted in Libyan wall sculptures dating around 1350 BC. The throwing knives were extensively collected by Europeans with the result that many European and American museums have extensive collections. However the collectors generally failed to record the origin of the blades or their use. As a result, the history and use of the throwing knives is poorly understood. A further complication is that the label Throwing knife was attached by ethnographers to various objects that didn't fit into other weapon categories even though they may not have been thrown. Western tradition Throwing knives are commonly made of a single piece of steel or other material, without handles, unlike other types of knives. The knife has two sections, the "blade" which is the sharpened half of the knife and the "grip" which is not sharpened. The purpose of the grip is to allow the knife to be safely handled by the user and also to balance the weight of the blade. Throwing knives are of two kinds, balanced and unbalanced. A balanced knife is made in such a way that the center of gravity and the geometrical center of the knife (the centroid) are the same. The trajectory of a thrown knife is the path of the center of gravity through the air. When a balanced knife is thrown, the circles described by the point and the end of the hilt as the knife rotates about the center of gravity will have the same diameter, making the trajectory more predictable.