Intshayelelo:Ii-purlin zensimbi zisetyenziselwa ukuxhaswa kwesakhiwo kwizakhiwo zesakhiwo sensimbi.Ngokuqhelekileyo, i-purlins zizinto eziphambili zezakhiwo zophahla.I-Roof purlins ixhaswa nokuba yi-rafers okanye iindonga zesakhiwo kwaye umgangatho wophahla ubekwe phezu kwee-purlins.