Equally versatile are screened jalousie panels, which can be cranked shut in a flash against a sudden sprinkle; while they are somewhat more expensive than self-storing panels, they allow for greater areas of open screening and thus more air circulation on pleasant days.

For regions with relatively constant weather, single-view panels serve well; they consist of a frame and a large piece of interchangeable glass or screen - but the glass has to be removed and stored while the screen is in place. They are not recommended for families with young children, since the glass extends almost all the way to the floor and can be a safety hazard.

All three sorts of panels - plus the attendant hardware - are readily available in aluminum finish or white; some manufacturers also offer a variety of baked-on enamel colors.

While panels are available in virtually any width, those less than 40 inches wide are easier to handle and sturdier than larger ones. Heights normally range up to 89 inches. For porches taller than 89 inches, oversized panels can be ordered or aluminum and glass transoms can be added above each panel to fill the space. If the porch is gabled, the triangular opening between the roof support and the roof is closed by nailing up siding or exterior-grade plywood sheathing.

The first crucial step in enclosing the porch is to outline and measure, with the air of chalk lines and a plumb bob, each wall opening - that is, each space between existing posts, or between a post and the side of the house. Once the vertical and horizontal dimensions of each wall opening have been determined, you can quickly calculate the size of all the needed components. Most porches are sloped for drainage, but you will not have to buy different-sized panels to compensate for the incline of the floor; wherever the walls need to be slightly taller, the panels can simply be raised within the 2-inch-deep channel that secured their base.

Doors can be positioned anywhere in an enclosure wall, but they require advance planning at the time that basic panel sizes are being calculated. Operating doors can be the same style as the wall panels or they can contrast.

When installation is complete, dab a bit of caulking along the base of the wall and into any small gaps where panels meet the side of the house. With these last protective touches, the glass will keep out chilly winds and will trap the sun's heat to extend the use of a patio room several weeks into cooler seasons. And in the summer, with the screens in place, the room will be cool, airy and pleasantly bug free.