I really like hanging around behind grocery stores, drugstores, seeing what they are throwing out (or very carelessly storing ... I'm not sure which it is sometimes) and I always see these wire shelf pieces that wouldn't normally work without their proprietary system in the store, and wonder how they can be hacked, also I needed some shelves to hang in my sunny windows for all my seedlings and figured the shelves would block the least amount of light.
I could see these being useful out in the garden, camping, anywhere you cant drill into a wall but the ceiling would be OK, great for inside closets too.
Step 1: Get Yer Shelves
Try going behind walgreens and target and such, keep an eye out and you'll see em. I like to affect a casual "mmm hm hmmmm oh look shelves in the trash? I guess I'll just take these . . . " attitude, you dont want to get caught looking like you know are doing something wrong just in case someone has a problem with you taking them (in all likely-hood I don't really think the store wanted these since some were bent, or they think no-one will take them because they wouldn't be useful w/out the proprietary supports) I feel this is a gray area to worth investigation. I might not investigate this at a smaller family establishment, or at least then I would ask first.
Step 2: Your Needs
some suitable rope or other linear element (chain would be nice)
A lighter to finish your ends if your rope is the melty kind
a stool or step ladder
a measuring stick or tape
Tie up your ropes from 4 points, preferably on intended site, use hooks and stud finder as needed if you dont have a handy beam like I did.
Use the ladder or stool to position your shelf near where you want it to end up so you can tie it with greater ease.
Step 3: Knots
I'm sure someone knows of a better knot but this was for my purposes easy to slide up for adjustments but did not slide down when weight was on shelf, please enlighten me if you have a better way.
See knot steps on pics below, and if you will be putting heavy things on your shelves you may want to put your ropes closer to the center.
Step 4: Measure and Level
Measure with your ruler or an object (preferably what ever you intend to keep on your shelf to get your spacing. Use your level to adjust all the knots so that your bubble is in the middle, it's tricky on the first one but starts to go very quickly as you get the hang of micro adjusting the knots.
Step 5: Repeat
Repeat as needed, and unhang and install as needed if you did not have the forethought to install in place. Hey nomads see how nice they fold for storage? Next time I will tie ropes closer to center to prevent bowing, but the plants are happy.
Oh yeah and the plants are growing in "ghetto greenhouses" https://www.instructables.com/id/EZUYT3RD9XEWT14K3U/?ALLSTEPS