"I-beam" shelves: 43" W. x 70" H. x 10" D.
Sturdy shelves cantilever off a central I-beam and can be adjusted to anywhere on the beam by gently tapping on supporting wedges. The shelves can point in either direction.
Shown here are two versions, one uses white ash (stained gray) for the beam and the other is made with cherry. The shelves are a "torsion box" construction that gain strength from their use of tempered hardboard glued to a wooden grid.