Cal Rutstrum, a canoeing author from early last century, made "camp refrigerators" with them. He built a small, stick framework near a stream, and would make a stick shelf in it. He'd set food on the shelf, and drape a wetted burlap bag over the rig. One end of the bag would hang down into the water a bit for wicking. Evaporative cooling helped prolong the food's useful life.