Ib lub tshuab purlin yog lub tshuab uas ua rau cov huab tais xis.
Purlins yog cov tswv cuab kab rov tav khiav ntev ntawm lub ru tsev, nyob saum toj cov rafters thiab txhawb nqa cov raftary rafters. Hauv cov tsev nyob deb nroog, lawv tau siv los txhawb cov rafters thiab ua cov kab rov tav ntawm lub ru tsev. Lawv yog ib qho ntawm cov qauv tseem ceeb ntawm ib lub tsev, tseem hu ua purlins. Ntawm lub ru tsev pitched, lawv feem ntau tso rau ntawm lub ru tsev trusses lossis kab pheeb suab, nrog cov vuas thiab cov vuas txuas ntxiv rau cov dej {}} penellent cov teeb.
Vim yog lawv lub durability thiab tus nqi - ua tau zoo, cov suab paj tsib tau siv ntau dua li cov ntoo thiab cov qauv steel.