Children love having their own special play areas out of doors. "There's something exotic to a child about having an exclusive spot to himself," says an award-winning playground designer, M. Paul Friedberg. Most parents agree and provide this designated child spot -- then fill it with the standard metal swing set.

They could do better, playground designers say. They recommend shopping at surplus and hardware stores, and going to a junkyard for cargo nets, parachutes, ropes, ladders, tires and mop handles. Using these, parents and children can work together to create a back yard that stretches imaginations and muscles to their fullest. (Or, as an alternative, high-quality, creative equipment could be bought -- but this is a more expensive alternative.)

Doing it yourself may result in a safer play area, using metal equipment. A recent study by the U.S. Consumer Product Safety Commission found that the safest outdoor equipment is also the most flexible, allowing for more than one activity at a time.

When you and your child design your own equipment, the creative ideas should flow freely. Any you later decide you don't like can be penciled out of the plan. Ideas for large equipment designs abound in Friedberg's books (check your local library). On the other hand, Melanie Lund, of Alexandria, filled her entire back yard with snazzy kiddie sets she designed by "walking around the hardware store and seeing what they had."

Her equipment provides challenges for both her children -- Sophia, three, and Rowena, two -- and she analyzes their play to see when they are ready for more. Her ideas, and those of professional landscape architects, include: CLIMBING. Eequipment can be as basic as the backyard tree or as fancy as one of Friedberg's structures. Mrs. Lund made a rope climber, using two trees grown close together, by zigzagging nylon rope through pointed eye hooks driven into the trees. Another of her multilevel structures uses various lengths sawed off an old tree and anchored into the ground to form a wooden "fort." To one of the larger tree slices, she attached a sturdy, wide board covered with metal flashing; this "wide slide" goes inside during the winter, where it rests on the Lunds' basement stairs. QUIET AREAS. Children cherish nooks where they can absorb the world or reject it, such as a tree house or the area under the porch. Tunnels made of metal barrels, concrete pipe or old tires set in the ground make cozy cubbyholes -- and many of these are free from salvage yards.

The Lunds' next-door neighbor provided their retreat. Using an old sheet and broom handles, she fashioned a tot-size tent that Mrs. Lund slings between two trees. SAND. The standard raised box is a fine container, Rick Heydt, a Fairfax landscape architect, says. Another good sand container, he suggests, is a "pit dug in the ground, with a good drain at the bottom." Surrounding the pit, to keep the sand in and provide seating for its users, you might carry out an idea suggested by Jay Beckwith, another playground designer:

Work with your children to arrange sacks of concrete into a design for a wall, strengthening the sacks with steel pipes. Once the design is set, thoroughly wet the concrete. Plaster the hardened surface and let the kids paint it or decorate it with mosaics -- shells, junk jewelry, pretty pebbles. SWINGS. The Lunds' back yard includes three swings: a toddler's seat for the two-year-old, hung with short ropes; a tire swing made from a neighbor's giveaway; and a wooden seat hung on 30-foot nylon ropes.

Mrs. Lund advises swing enthusiasts to paint their wooden seats with a simple wood stain. "We tried latex paint, but the kids kept slipping off," she reports.

This year the toddler's seat keeps her kids secure; but next year she plans to take it down and substitute a steel bar to develop her children's trapeze skills. PATHWAYS AND HOT WHEELS. When you design your child spot, keep in mind what paths your children will take -- both the paths you authorize and those they devise. Circles, diagonals and curves soften restrictions placed on children by formal pathways.

Keep the walks interesting, and make sure they go somewhere, so your kids don't "bottleneck" at one end. And provide for tricycles, kiddie cars and disco rollers by using ramps instead of steps, and by linking all pathways.

Finally, take a fresh look at every aspect of your yard and try to see all its potential. Is the patio a possible circus ring? A speedway for big wheels? How about the fence -- can you climb it?

Looking through the eyes of a child, you may foresee and prevent a few problems. And, more important, you may discover a few opportunities for back-yard creativity that you never realized you had.