Sleek shapes and taut surfaces give shade sails a dynamic presence that belies their practical mission. In the West, these tensioned fabric canopies represent the latest in backyard sun protection. The idea comes from Australia, where, years ago, canopies were made of sailcloth. Now architectural sails are made of high-tech synthetic knits that wear better and block out more UV rays—up to 95 percent with some fabrics.

Economy, not just style, will soon make shade sails more common in the United States, predicts John Reisinger of Reisinger Rigging ([XLINK "http://www.reisingerrigging.com" "www.reisingerrigging.com"] or 909/364-1705), which installed the project shown here. “Per foot, it’s the cheapest form of permanent shade there is,” he says. “Sails are also versatile enough to go with most architectural styles, and they’re a breeze to take care of. Just hose them off.”

Ready-made sails you install yourself start at about $130 for a 12-foot triangle. Large custom-designed sails and installation run several thousand dollars and up. Shade Sails ([XLINK "http://www.shadesails.com" "www.shadesails.com"] or 562/945-9952) offers made-to-order and ready-made options. Coolaroo ([XLINK "http://www.coolaroo.com" "www.coolaroo.com"]), an Australian firm, sells ready-made sails. —Sharon Cohoon