Ziyini izibani zenkungu? Umehluko phakathi kwezibani zenkungu zangaphambili nezangemuva?
Izibani zenkungu ziyahluka ezibanini ezisebenza ngesakhiwo sangaphakathi kanye nendawo enqunyiwe. Izibani zenkungu zivame ukubekwa phansi emotweni, eseduze nomgwaqo. Izibani zenkungu zine-Angle enqunyiwe yokukhanya phezulu kwendlu futhi zenzelwe kuphela ukukhanyisa umhlabathi phambi noma ngemuva kwezimoto emgwaqweni. Esinye isici esivamile ilensi ephuzi, isibani sokukhanya esiphuzi, noma kokubili. Abanye abashayeli bacabanga ukuthi zonke izibani zenkungu ziphuzi, inkolelo-mbono yobude besikhathi obuphuzi; ukukhanya okuphuzi kunobude besikhathi obude, ngakho-ke kungangena emoyeni ojiyile. Umqondo wawuwukuthi ukukhanya okuphuzi kungadlula ezinhlayiyeni zenkungu, kodwa kwakungekho idatha yesayensi eqondile yokuhlola lo mbono. Izibani zenkungu zisebenza ngenxa yendawo yokufaka kanye ne-Angle eqondiwe, hhayi umbala.
