The cabin had a fully stocked kitchen, electricity and a screened-in porch overlooking the Massanutten Mountains. Not bad for a little weekend retreat.

Cost: Nothing.

Reservations: Just one telephone call a few evenings before the Saturday morning of the excursion.

Guaranteed: A sumptuous Saturday evening feast, under $5, surrounded by fall foliage and the stars that Washigton pollution usually hide.

And probably sore muscles and a solid Sunday night of sleep when you return to Washington. The law of the woods is quid pro quo.

The Potomac Appalachian Trail Club, a hiking and mountaineering group with more than 3,000 members, maintains a string of cabins, ranging from three-walled shelters to the relatively luxurious place with electricity, along the trail. Some are available only to club members; others are open to anyone who plans ahead, as they require reservations well in advance.

The way to get around this, and to meet a group of 10 to 20 people at the same time, is to help PATC on its trail work. In one of its craftier maneuvers, the National Park Service has ceded maintenance of large portions of the Appalachian Trail to hiking clubs along the East Coast. Some sections need only occasional sprucing-up and weeding to remain passable, but in other areas, sylvan paths are overgrown and rock-studded.

It falls to legions of beleaguered volunteers to turn rock into trail, and bramble into clearing. And it's the task of the PATC to bring method to the madness, at least in the area nearest Washington and to apportion the brawn as the work demands.

Trail supervisor Tom Floyd is a tall man from the Ozarks who doesn't speak often but is listened to when the words finally come. Each of about 150 other volunteers under him has responsibility for a small section within the PATC parcel.

"The overseers range from a father and son who do all the work themselves to people who see what work has to be done and then get other people to do it," he said. Any weekend, someone, often Floyd, organizes a work trip to the Appalachian Trail. The mood, he said, varies according to the group leader, the sleeping accomodations and the difficulty of the project.

It also depends on who decides to show up. On one recent trip, fewer than half the 13 volunteers had ever worked with PATC before. The work consisted mainly of weeding and clipping an already well-maintained section of trail.

There was Bill, who had just celebrated his 61st birthday while bicycling in Vermont, wearing a "Keep On Biking" T-shirt and huge hiking boots.

Jane took charge of the Saturday-night meal crew and concocted a dinner that left everyone very full and slightly tipsy.

"A few years ago, I would never be on something like this," she said. "I would be home being a businessman's proper wife."

The first-timers ranged from Jim, an outdoorsy type who seemed happiest when he was sweating over some particularly unmovable rock, to Debbie, who said she came to meet men. She left the group in a tiny Virginia town, before even reaching the trail, and took a Trailways bus back to Washington.

Conversation came easily to strangers working together at jobs usually thought of as labor for chain gangs. There's no pressure to work past the point of fatigue, but a volunteer should expect a few solid hours of toil on Saturday and Sunday afternoons.

Work-trip etiquette sanctions solitary walks into the forest and a little trailside romance. But a slouch who does no work is not appreciated. And a slouch who doesn't help with either the Saturday evening dinner preparation or the Sunday morning clean-up-the-cabin effort runs the danger of earning a reputation as a free-loading slouch.

Sometimes the leader undertakes construction of a shelter or a new trail. The purpose of another expedition in mid-September was to relocate a portion of the trail that now follows a Virginia state route.

It was heavy-duty stuff.

First the leader, Carl Solomon, showed the group how to build a trail. He raised a pick-ax above his head and began digging out rocks and roots from the dirt. He started to sweat. He started to breathe hard. Gradually, a path the width of the ax handle emerged.

He looked at the group gathered around and smiled winningly. "And that's all you do," he said.

"I'm going to take my grandchildren out here," said Virgil, a broad-shouldered carpenter who has many years to go before grandparent age. "I'm going to show them that I made the Appalachian Trail."

Unless it rains on a Saturday, a frequent occurrence this season, most of the work gets done on the first day.

Sunday afternoon, Carl's group spent most of the afternoon over a lazy lunch next to a stream. One group napped in the sun, a few others talked about goat cheese and a third contingent mainly just ate.

"By Sunday after lunch, I know I'm leaving soon and I think I work accordingly," said Carol, as she alternated hoisting a pick-axe with chatting. She started going on PATC trips as a way of getting out of town. "The friends in my office ask me what weird thing I did this weekend," she added. "But it feels good to be able to say that I did something besides sitting around the house." ALONG THE TRAIL When the snow fell on leaf-laden trees several weeks ago, many areas of Shenandoah Park suffered greatly. Volunteers are always welcome, but they'll be especially appreciated now to help make the trails passable.

The Potomac Appalachian Trail Club has an office at 1718 N Street NW, open weeknights from 7 to 10. Maps of area trails and publications about backpacking and hiking are on sale.

The club publishes a monthly newsletter that lists a schedule of upcoming events -- work trips, hikes, courses held at the headquarters. Mountaineering, rock-climbing and cross-country skiing sections of the club have also been formed on the initiative of individual members.

For details, call the club at 638-5306.