"Lega masks are used as initiation objects in the Bwami society of the Democratic Republic of the Congo. Masks are divided into five types according to material, size, and form: lukwakongo, kayam-ba, idimu, muminia, and lukungu (Biebuyck 1973,164). They serve as an important mark of rank, identifying the owners as members of specific Bwami levels.

Unlike many masks in other African cultures, the masks of the Lega are not usually worn over the face, they are attached to the body, held in the hand or
simply hung on fences during the initiation ceremonies of the Bwami society."

http://www.randafricanart.com/Lega_mask.html