Dirty Shelves can be hung on the wall up side or down, used as bookends and are made of landfill-bound plywood waste.

+ ref-use.com

"These dirty little shelves can be hung on your wall with the level side up, which offers a flat surface for any ol' thang you could think of... Or, they can be hung with the uneven side up, and suddenly you have built-in bookends for your extensive library. All ref-use products are made with landfill-bound plywood waste, and finished with non-toxic/low VOC stains, paints, and topcoats."