Here's how the pre-fab trusses were raised:
Click here for a quick technical explanation of this process.
Nowhere in any technical explanation of this process does it say to order 2 six-packs of beer with a pizza lunch for two men with bad backs climbing on scaffolding to affix trusses over concrete slab. When I strongly objected to the liquid portion of the lunch order, I was dismissed and overruled.
But there was the structure at the stage that it was, and it had to be finished, so things proceeded but less happily than before.