"These Ngala swords from Zaire, with their unique form of sickle-shaped blade, were sometimes used for a particularly gruesome form of execution. The victim was secured to the ground with his head tied to a supple tree bent over for the purpose. At the moment of decapitation the head was catapulted into the distance."
* Withers & Capwell 2010 p79
"Congolese Ngala knives appear in three main forms. The first is very long, double-edged and curved in a shallow, graceful arc. The second is shorter and wider, the blade often tear-shaped with one or two ridges. The third is almost a form of machete -- wide-bladed and long, decorated with ridges, profuse file-lines and cross-hatching. The leading edge is recurved and the trailing edge cut into a series of cuspings, the point forming a stout hook. These knives were often taken to be decapitation implements, but are more likely to have had ceremonial significance. Closely related to the Ngala knife is that of the neighbouring Ndjembo. This is of similar length but straight until it divides into two long points that curve inwards in a crescent shape."