Is this an illusion?

Can someone tell me how this underlayment is attached and why those bundles don't slide off.

It's actually refreshing to see a guy working without ropes around his neck, but I have to say I would never carry a bundle on my shoulder on that pitch. Lower the center of gravity and carry them with two hands. That's my opinion and I'm sticking to it. I would never load that way either. They should be resting against the stickers. They make brackets for 2X4's laid flat. Very light, very easy to install. Why risk a chain reaction that tears the gutter off the roof. jmo.

Good 30# installed with a bunch of slap staples. "cts racing" is right about the nails holding the bundles[size=3][/size]

2 sided grace I&W :woohoo:

My guess is there is a 8d / 16d nail at the bottom of each package.