Ngenxa yeenzuzo zayo zokuvelisa kwayo ngobuninzi, ulwandiso loluhlu lwesicelo lubanzi, ukusuka kwisicelo seglasi yokuslayida kwiglasi yodonga lwangasemva.Kuba imilo yevili lokusila inokutshintshwa, isipili somkrolo wesithuthi sinokuvela neemilo ezininzi ezahlukeneyo zemigca.