“Outside cats” are a politically incorrect breed these days. A myriad of concerns – from communicable diseases such as Feline Immunodeficiency Virus to the possibility of being hit by a car – prompt responsible cat owners to keep their kitties in the house.

But, as common sense should tell us, there’s no indoor substitute for fresh air and sunshine. And some creative owners have come up with ways to contain their cats while giving them a chance to exercise their God-given right to stalk bugs and sun-worship for hours.

“It’s a relatively new idea for people to construct enclosures and playpens for cats. But it’s a safe way to let them enjoy the benefits of butterflies and birds,” says cat behaviorist Marva Marrow of Hesperia, Calif. “I’m seeing some beautiful solutions, such as gazebos with screens that were fit into people’s gardens in harmonious and aesthetic ways.”

Cat enclosures are a snap for do-it-yourselfers. One approach is to construct a frame out of two-by-fours, then enclose it with poultry netting, chicken wire or chain link. (Be sure to create some sort of a door so you can have access.) Ambitious souls can engineer it so the cat has access from a kitty door or open window in the house.

Homeowners with screened-in porches have ready-made enclosures that their cats can enjoy. Apartment dwellers with balconies and porches can find ways to screen and kitty-proof them, too.

Marrow builds inexpensive but hefty outdoor enclosures out of wire-coated shelving often used in closets.

“You can build them to your own measurements and specifications, and they become free-standing enclosures,” says Marrow, who uses plastic cable ties to lash the panels together to make sides and a roof. She also uses them to fashion bay-style build-outs attached to windows, so the cat can go out whenever he wishes. (Sometimes a wire dog crate can be retrofitted for this purpose as well.)

For couch potatoes, the great outdoors can be a little overwhelming at first. “If they’re not used to it, they’re paralyzed with bewilderment,” Marrow says. “Then a butterfly comes by, and all of a sudden they’re really energized.”

No matter what your blueprint or materials, keep the following in mind:

Think vertical. Cats are climbers, so they appreciate different levels and lofty perching spots. Try cat trees, or stout branches from the real thing. Because they are height-bereft, cat tunnels are only “marginally interesting” to the twitchy-tailed set, Marrow notes. If you must have them, use them to connect one vertical enclosure to another.

Nurture your green thumb. You can plant lots of kitty-friendly plants in and around your enclosure. Consider aromatic but safe plants such as lavender and that all-time feline favorite, catmint, which self-seeds generously.

Beware of gaps. Cats can be crafty escape artists. Make sure your enclosure is securely anchored, with no gaps. “If cats can get their head through something, they can usually get their body through, too,” Marrow warns.

Be shady. While cats love to sunbathe, they also need a refuge from extreme heat. Marrow puts a shade cloth over a portion of her enclosure.

Provide water. Water-circulating foundations are appealing to many cats. If you want to make food available, Marrow suggests placing the food dish inside a larger, water-filled dish to prevent ant invasions.

Remember nature’s call. If your cat doesn’t have access to his inside box, place a small sandbox in a sunny corner of the enclosure.

Consider the humans. If the enclosure is large enough, think about features that would make it inviting to two-leggers, such as lounge chairs or maybe a hammock.

If you’re not handy, these Web sites offer prefabricated or custom cat enclosures:

bandobi.com, 714-227-1733

catfencein.com, 888-738-9099

cdpets.com, 707-763-1654

outbackbarneys.com, 800-967-5604

petsamaritan.org/Help/catrun.htm, 801-966-3120

playscapesforpussycats.com, 512-828-7000

purrfectfence.com, 888-280-4066

safekitty.com, 207-929-4128

thecatsden.net, 416-466-8930

ultraliteproducts.com, 888-858-7298