The supports are long steel bars that go through the shelves and into the studs in the wall. We predrilled holes for them before we tiled. We used oak planks seamed together to make a solid wood shelf." I love the hanging coffee mugs.
We've used a similar corner shelving unit to create space in a small 7 by 9 ft room. It's a great, easy shelving solution for small spaces (although installing it was a bit tricky as the walls weren't plumb.