I first used a Thelma fly in Yellowstone in January of ’84 and have used this extraordinarily versatile piece of camping gear in many situations since then. They are manufactured by NOLS (National Outdoor Leadership School). I rarely take a tent when I go camping, and instead just take the fly. I use it for car-camping, backpacking, or even just for shade at the beach. Unlike many flys, this one is large, 13′ long x 9’2″ wide, and well designed in that it has many guying points, crucial for keeping out the weather when things get a little dicey. It sleeps three easily with lots of gear.
I’ve used it car-camping, sea kayaking, in -30 conditions, and in the desert. Its uses are only limited by your creativity: cook in the shade or out of the rain, fill up the eave space with snow for winter, attach to a tent doorway and have plenty of space to de-layer before getting into the tent. Only 4.7 pounds and very long wearing. Most other flys aren’t large enough or have too few or too flimsy of guying points to be as useful as the Thelma fly. My current one is over 10 years old.