Pali mitundu yambiri yamakina njerwa pamsika, yomwe ili mu makina a njerwa yotchedwa konkrite block. Koma kodi mukudziwa za chizindikiritso cha makina ogona njerwa? Kodi mukudziwa zomwe zilembo za njerwa zikuyimira?
Kukula kwa block ndi njira yofunikira mu malonda omanga, kuphatikiza kulengedwa kwa mabatani a konkriti omwe amagwiritsidwa ntchito pomanga. Tekinolojiyi yasintha kwambiri kwa zaka zambiri, yoyendetsedwa ndi kufunikira kwa mtengo - Ogwira ntchito okhazikika komanso olimba