Iyunithi yokuqala iyafana neyesibili. Uma wengeza amanzi iyunithi ingasetshenziswa ukususa impushana yokuphrinta. Iyunithi yesibili iyidizayini enamarola amathathu, i-roller yayo yerabha ethatha izinto ezithile ukuze ikwazi ukumboza ngokulinganayo umkhiqizo ngomphumela omuhle. Futhi ifanela uwoyela osuselwe emanzini/osuselwe kumafutha kanye nevanishi yebhamuza, njll. Iyunithi ingalungiswa kahle ohlangothini olulodwa.