I just put tar paper underneith the metal and used screws-( I would'nt use nails) to attach it, The way I cut it was tin snips, yes it was a pain, I pre-driled the holes and it went up slick./w3tcompact/icons/smile.gif I don't know if this is a real benefit but , I did use 5/8 plywood for my roof- my reasoning was that 1/2 flexes way too much and that is what kills a roof.