Page 8 mislabels rivets as screws. They are not screws. They are an alternative fastening method.
A rivet is a cylindrical metal tube that deforms into a crimp as a mandrel is pulled through it.
Not trying to be a smartass, but I just thought to note the original rivet doesn't have a mandrel, being just a solid piece of metal. It's hammered in the locked form from the other side. Mandrels came with pop rivets, so that you don't need access to the other side. Both are still used today, depending on the work to be done, even if welding has very often replaced rivets of all types. But yes, I assume pop rivets were used in this case, so you are absolutely correct and I'm not trying to deny that.