Be advised that "fudding" is a serious matter to Macon Reed Jr., its creator.

A fud, he says, is the number of aluminum cans a good man with one pair of tongs can collect in an afternoon, given standard conditions of temperature and weather.

He calls the activity fudding. A fud converts, he says, to approximately 7.1952 English pounds.

Reed, a retired Washington newsman and self-taught computer expert, can be found on almost any day, a 36-inch-long pair of homemade, scissor-action tongs in hand, picking up somewhat less than one fud of cans in the vicinity of 4th and G streets SW. He calls it "going fudding." This is his 10th fudding year.

Proper attire appears to be blue jeans, Hush Puppies and, for variety, a computer printout stuck in a shirt pocket. Half-moon glasses dangle from a black cord around Reed's neck. He has shaggy gray hair, a bulbous nose and hazel eyes.

One may well wonder about the state of his mind. Ask him, and he will say he is working for the Association for Environmental Piety (AFEP). It is an organization of one: He is the only member.

Be persuaded that Reed is not crazy.

"He's not an MO," observed Officer G. L. Thomas at the First District Police headquarters, 4th and E streets SW, using police lingo for a person needing "mental observation."

Most officers there are dimly aware of Reed's activities cleaning up around their compound.

"He doesn't bother nobody," said Officer M. J. Durham. "He's got more scissors than I've ever seen in my life: blue ones for Tuesday, yellow ones for Thursday . . . "

Most days Reed spends 45 minutes with his elongated scissors making regular rounds from his apartment building at 301 G St. SW, going under the Southwest Freeway, then behind J. J. McCallum's Gulf station, around the First District police station, and half way down School Street.

His "office" is a wheel-less blue van behind the gas station. A true can aficionado, Reed can tell by the folds of a crushed pop can whether it is real aluminum or a steel imposter. If it is aluminum, it is carefully saved in a plastic bag. When enough fuds are collected, AFEP sells the cans to recyclers, if its member can borrow a car. More often, AFEP donates the collected aluminum to the National Black Veterans Organization, Inc., 629 F St. NW, to boost its treasury.

Reed does not stop with cans, however. Once you're in the can business, he said, you're really in the trash business.So he filches empty barrels from a lot behind the nearby Capital Film Laboratories, Inc., paints them (blue or red), pries holes in the bottoms (for drainage) and places them at strategic locations on his rounds.

Then, regularly, he empties them, showing a recent visitor with evident delight and satisfaction that his trash cans are really used by passersby and that the three block area he polices is noticeably cleaner. All in all, he said, the task is his "sure-fire bit of virtue."

Although trash activities occupy most of Reed's time, at home he helps his wife, Jean, type the crossword puzzles she constructs for The New York Times. Together they love words, and own four unabridged dictionaries.

Reed says he passed the Virginia bar examination in 1933, but made journalism his career, working for several newspapers and radio networks. After retiring in 1970, he delved into computers and taught himself to program. He devised several complex computer programs, including one that teaches a computer to play seven card draw poker with itself.

Reed may not be an MO, "but the thing you don't know is to what extent Macon is putting it on," cautioned John J. Ford, staff director of the House Armed Services Committee and an old Reed buddy.

"He's clearly a very intelligent man," offers Art Jaeger, press aide to Rep. Gladys Noon Spellman (D-Md.), another Reed devotee. "He's sort of the ultimate individual. He does what he wants and he doesn't much care if people think he's crazy."

Press Reed on his can and trash venture and he is hard to pin down.

"It has a certain amount of show-off value," he jokes. But he waxes serious for a moment, allowing a glimpse of his real motivation.

Sitting on the grass in a neighborhood park clutching his knees like a 10-year-old, he says, "Most people limit themselves to righteous indignation" about environmental matters. "That's the cheapest emotion I know."

He has even attracted some parttime fudders.

"At first I didn't know what his story was," says Sarah Wells Duffy, 26, a lobby researcher and sometimes fudding partner. "But pretty soon we became pals. You know how some old people start acting young. He didn't seem to be acting young. He just acts Macon."

It seems just about everyone who knows Reed is a fan.

"You're not going to find the other side of this story," warns Robert Horowitz, a longtime friend who is editor of The Montgomery Journal. "There isn't one."