Every 6 to 8 feet in the attic I saw this “reversed porcupine” cluster of nails. Never saw this before. I thought it might be a method of nailing a strap/plate to keep the sheathing tight, but when I looked up into the crack between the boards I could see the underlayment. Any thoughts?:-k
Are they staples or nails? Looks like staples from the picture.
-Carl
I think they are staples.
Framers air stapler was giving him grief so he was slapping the stapler on the roof getting it going. Just my WAG.
"Psst…The boss is looking…"staple staple staple staple 
In other words, I have no idea
-Carl
LOL – That was my first impression too, but there were several areas like that regularly spaced.