Igiceri cy'icyuma, kizwi kandi nk'icyuma gikonje.Ibyuma birashyushye kandi bikonje bikonje.Mu rwego rwo koroshya ububiko no gutwara, no koroshya gutunganya ibintu bitandukanye (urugero, gutunganya ibyuma, ibyuma umukandara, nibindi) Ibiceri bishushanyije, cyangwa ibyuma bishushanyijeho, byitwa kandi ibyuma bisubira inyuma, aribyo byuma bifite rombus cyangwa imbavu. hejuru.Bitewe nimbavu hejuru yacyo, icyuma gikozwe mubyuma gifite anti-skid, kandi gishobora gukoreshwa nkigorofa, escalator yinganda, ikariso yakazi, ubwato bwubwato, hasi yimodoka, nibindi. Ibisobanuro byibyuma byagenzuwe bigaragazwa mumagambo y'ububyimbye bwibanze (utabariyemo ubunini bwurubavu), kandi hariho ibintu 10 byihariye bya mm 2,5-8.No 1-3 ikoreshwa mubyuma byagenzuwe.