Hem the weatherproof fabric and use industrial thread to sew 1-inch steel rings at the top 4 points where the curtain will attach to the poles. Repeat using 1.5-inch rings at the middle and bottom points where the curtain will attach to the poles.
On the edge that will serve as the "door," sew on three swivel hooks. Slide the rings onto each tent pole, starting with the larger bottom rings (the smaller, 1-inch rings will sit atop the poles).
Hammer the poles 6 to 8 inches into the ground. To close the door, clasp the swivel hooks onto the adjacent pole. You can raise or lower the curtain's height depending on who is showering, and it can be washed and dried using industrial-size machines.
5 yards weatherproof fabric (such as Sunbrella "Donghia Maui" fabric, Boston Design Center, 617-449-5506)
Rinse away grit after a beach trip -- or a wrestling match with the mower. This outdoor shower hooks right up to your garden hose (yep, it's cold water only; for a hot-water shower, consult a plumber). Add biodegradable bath soaps, and hop in.
For the curtain, we hemmed weatherproof fabric, sewed on rings, and hooked them to tent poles.