It makes sense to copy the metal retaining walls from the other side so the synthetic canvases don't fall on the floor. Fortunately I had a great undisturbed source to copy from on the top shelf of the photographed side.
The metal grating was selected with a polygon mask tool and copied to a new layer. This new layer was placed just in front of the top synthetic shelf. Obviously the angle of the back side of the shelf is slightly different than the front, so the new retainer had to be stretched horizontally to match the angle of the back side of the shelf.
I could have created a little cast shadow on the shelf next to the metal retainer, but I decided it wasn't worth the hassle.