I used two large ones I got at yard sales for 50 cents each to make a mini greenhouse on my front porch in November (it's under a roof overhang facing south). Covered it with two layers of clear plastic shower curtains I got cheap at Big Lots and held them in place with clothes pins at the top. When it got super cold (down near 0) for several days, I covered all of that with another larger piece of plastic, anchored with pots of soil on the outside. I'll be darned if almost everything survived!
It warmed up over freezing yesterday so I peeked in and found I have spinach, kale, lettuce, mustard, celery, petunias and calendula still growing!