In the beginning, there were people, and they had things, and the things were good, and the people were happy. And some of the things were fragile, and some were sharp, and some had pointy knobbly bits, like a lego piece but worse, and people would step on these things, and this was not good.
And one day a person put the things up on a rocky ledge, and lo, they were not on the ground, and could not be stepped on, and there was much rejoicing, and yea, people had invented the shelf.
And people began to accumulate more things, but there were not more ledges, so they made new ledges with logs …