The other day, we passed a pile of bright blue plastic soda crates on the street and wondered what we could make of them —one of the pleasant mind games we play when spot raw materials for the taking. Not having time or the room, we passed them by. As often happens, we stumbled on a number of answers to our question: possibilities in the realm of plastic crates.
First, we remembered a simple use we’d seen in Union Square Park: an upturned soda crate set onto a plastic milk crate makes a perfect chess table, with milk crates also acting as seats for the players.

…(Plastic milk crates are endlessly useful, as portable planters for a milk crate farm, and as a sturdy, makeshift support for a bed frame hidden by a bed skirt, among other things).

Then we read about thirty architecture students who used 5000 recycled red crates to create an interactive structure in a pavilion at the annual book fair in Juarez, Mexico. This Social Topography Project invited visitors to use it in multple ways:“as benches to sit on, as a threshold that connects the fair isles, an observation platform to see other stands from another perspective, as stairs, a playground for kids, an amphitheater for a concert and as a place to hold a small lecture or conference.”

Apparently, the brightly-colored soda crates are often used as a “challenge” for designers to “up-cycle”. In 2012, Mexican studio BNKR Arquitetcura built a pavilion out of 5,000 plastic soda crates as part of the cafeteria for Expo CIHAC, the largest architecture and construction exhibition in Latin America. They snap together something like Lego’s (although they need ties for support).

via Design Boom
Anyone make a garden path with black plastic pallets?
I think the concern would be if you want to use them for edible plants as the plastic may leach.