Not only does it save space, but outdoors, a gutter planter off the floor will alleviate issues such as slugs, maggots, rabbits, and other wildlife that might feast on your leafy greens. For an out door space, it may make sense to drill drainage holes on the planters so excess water from your hose will trickle down.
Hydrponic raingutter lettuces taken in Philly, by beelaineo
For indoors, a rain gutter could nestle perfectly over a windowsill, serving as an herb planter, or an aesthetic garden for succulents.
Aluminum windowsill succulents by kalanikordus