Raised garden planter boxes on wheels / casters - Size is 2 x 4 each, just over 4 tall with the casters installed on the bottom. Soil depth container is 12 and the bottom shelf has about 3 of clearance to hold drain water trays.
Salvage Co. Australia: A Good Source For Reclaimed Hardwoods
DIY urban planter box plans - I have not considered anodyzed corrugated metal as a possibility for planter boxes. But it might make a fairly inexpensive building material. Wonder if it has any risk of leaching toxic stuff into soil for vegetable boxes?