Ibi birango by'ibanga akenshi biba bikozwe mu cyuma kandi bifite igishushanyo cyangwa ikirango kigaragaza ikigo runaka, ubukangurambaga, cyangwa ubutumwa runaka. Bikunze kwambarwa ku makoti, amashati, ingofero n'amasakoshi, kandi bimaze imyaka myinshi ari uburyo buzwi bwo kugaragaza no kwimenyekanisha.