Ibyuma byahinduwe ni ibyuma byubatswe hejuru yicyuma, bizwi kandi nkibyuma byimbavu, mubisanzwe bifite imbavu ebyiri ndende kandi imbavu zinyuranye zigabanijwe ku buryo burebure.Imiterere y'urubavu rwa transvers ni spiral, herringbone na crescent, Screw umugozi wicyuma nicyuma gikenewe mukubaka ibice hejuru yubunini buciriritse, kandi Ubushinwa bufite ibicuruzwa bimwe byohereza hanze buri mwaka.