Isingeniso:Ama-purlin ensimbi asetshenziselwa ukusekelwa kwesakhiwo ezakhiweni zesakhiwo sensimbi.Ngokuvamile, ama-purlins ayizingxenye ezinkulu zezakhiwo zophahla.Ama-roof purlin asekelwa noma ama-rafers noma izindonga zesakhiwo futhi uphahla lubekwe phezu kwama-purlins.