Lub qhov rooj hluav taws faib qhov chaw ntawm lub tsev mus rau hauv ob peb lub qhov hluav taws kub, yog li ntawd ib zaug hluav taws tshwm sim hauv txhua qhov hluav taws kub, nws tsis tuaj yeem tawm mus rau ib lub sijhawm, kom tswj tau qhov hluav taws kub zoo. Lub qhov rooj hluav taws steel muaj lub zog siab thiab kev tiv thaiv hluav taws zoo.