I hiked Mount Hoffman in Yosemite today and at the top there was this metal plate bolted to the rock with 4 metal rods welded to it. On the side you can also see some rivets so possibly there was something attached to it.
What could it be?
That is half of an old summit registry box. That one is missing the top and might not be the exact style but the full ones look like this.
Its obvious that its aluminum because it hasn't corroded and the point of the "rollers" is to keep the record book above moisture because the containers aren't waterproof. Unfortionaly, people steal and vandalize these boxes.