I-engeli yensimbi, ngokuvamile eyaziwa ngokuthi i-engeli iron, iyinsimbi ende enezinhlangothi ezimbili ezibheke komunye nomunye. Kukhona insimbi ye-engeli elinganayo kanye nensimbi ye-engeli engalingani.Ububanzi bezinhlangothi ezimbili zensimbi ye-engeli elinganayo buyalingana. Ukucaciswa kuvezwa ngo-mm wobubanzi obuseceleni × ububanzi obuseceleni × ukujiya ohlangothini. Okufana nokuthi “∟ 30 × 30 × 3″, okusho ukuthi, insimbi ye-engeli elinganayo enobubanzi obuseceleni obungu-30mm nogqinsi lwaseceleni luka-3mm. Ingabuye ivezwe ngemodeli. Imodeli iyisentimitha yobubanzi obuhlangothini, obufana nokuthi ∟ 3 × 3. Imodeli ayimeli ubukhulu bogqinsi bonqenqema obuhlukene kumodeli efanayo, ngakho ububanzi bonqenqema nobukhulu bonqenqema bensimbi ye-engeli kufanele igcwaliswe ngokuphelele inkontileka neminye imibhalo ukugwema ukusebenzisa imodeli yodwa. Ukucaciswa kwensimbi ye-angle yomlenze olinganayo oshisayo ogoqiwe ngu-2 × 3-20 × 3.