same question!

You bore holes in the brick wall that go into the support studs. Metal bars go into the holes, likely with some sort of epoxy to hold them in place within the stud/beam. Then, you bore similar holes into the wood shelves that match the distance & placement of the metal bars protruding from the wall. I'd use epoxy when sliding the shelf into the wall-mounting bar too. End result = there's no visible support apparatus. Its hidden witin the shelf itself. Makes for an industrial yet very clean look. Not too hard; just takes some planning. If you do searches for industrial pipe shelving, you'll see similar ideas where the support is NOT hidden at all, but used as a proper structural and cool design motif at the same time.