When Jody Powell stepped out of his car in front of the Edwin C. Cregger Jr. American Legion Post No. 168 here Wednesday afternoon, the momentous event was recorded by no fewer than five television cameras.

The presidential press secretary flashed his boyish grin - a feat he is still capable of even after 20 months as Jimmy Carter's chief spokesman in Washington - and dashed for a side entrance of the gray , stone building.

It is only six miles from here to Camp David, the secluded presidential retreat in the Catoctin Mountains, but it might as well be 6,000. For the next several days, Powell's daily appearance at the Legion hall - literally a descent from the mountaintop - is likely to be the event around which the lives of some 400 reporters, photographers and broadcast technicians revolve.

In the meantime, there is very little to do as the journalists sit and wait for even the most trivial tidbit of information about the deliberations of President Carter, Egyptian President Anwar Sadat and Israeli Prime Minister Menachem Begin.

"Have you ever seen anything so incestuous," someone said on the first day. "There are people shooting film of people shooting film of people shooting film."

Indeed there were, and there was more. There are local reporters here interviewing some of the better-known national correspondents. There are national reporters and foreign journalists interviewing local townspeople, dredging the collective memory of Thurmont for recollections of Winston Churchill, Franklin D. Roosevelt and others who have passed this way before.

The high point of this kind of journalism occurred Wednesday afternoon when an Israeli camera crew spent several minutes filming still photographs of the summit participants that had been taped up on a wall of the Legion hall.

With so many people having so little to do, tensions are bound to mount. The Middle East summit conference was only a few hours old when the first territorial dispute erupted. It involved not the West Bank of the Jordan River but western Maryland.

The local editors of the Baltimore Sun were outraged to learn that one of the newspaper's Washington-based correspondents had written a story about Thurmont. Yesterday, they dispatched one of their own men, presumably to do the same thing.

But even with the approaching boredom which so far has lived up to its advance billing, there is always a sense of excitement where the heavies of the news media gather. It is not every day, in Thurmont or anywhere else, that you can see an obviously bored-to-death David Brinkley being interviewed or Barbara Walters hunched over a table scribbling who knows what into a notebook.

And the media represent publicity and that can be valuable.William S. Bivens, the director of something called Digital Systems Corp. in Walkersville, Md., was around here Wednesday telling reporters about his latest computer innovations.Federick County Democratic State Central Committee, left one of his campaign cards on some of the cars in the parking lot across the street from the Legion hall. And yesterday Carol Levitt, who operates a delicatessen in nearby Federick, called the Thurmont press center and asked for anyone from The Washington Post.

"We were reading about how everyone is bored up there in Thurmont,"she said, announcing that the deli was featuring Jewish and Middle Eastern food this week, that the entire press contingent was more than welcome or that food could be shipped to Thurmont.

Many of the reporters have probably never heard of Thurmont, Federick or any of the other towns that dot the gentle mountains around Catoctin State Park where the future of the Middle East is possibly being discussed. They have come not just from the United States, Israel and Egypt, but from around the world - Britain, France, Germany, even Brazil. Every day, after Powell's briefing, the paneled auditorium of the Legion hall is filled with a babel of voices in a half dozen or more tongues.

"I've called places on this earth I've never heard of," one of the long-distance operators serving the press center said in wonderment yesterday.

We are all talking into the telephones, but we are not saying anything because there is nothing to say.

There is nothing to say because the Americans, at least, want it that way. The journalists were warned in advance that there would be little or no information made public about the summit discussions.

The theory is that a virtually total ban on news will make the business of the meetings all that much easier to conduct. There is no use worrying about how it all looks to the outside world, because the outside world doesn't know what is happening. There is no sense in posturing for domestic political consumption, for there is no one to posture to.

So far, Powell said yesterday with obvious satisfaction, it seems to be working. The American press secretary has his own tripartite agreement with his Egyptian and Israeli counterparts, and It, too, seems to be holding up. So far, Powell has done all of the talking with the other two nowhere in sight.

To keep the news lid on as tight as possible, virtually everyone who knows anything of the discussions, including the press secretaries, is staying inside Camp David creammed into overburdened facilities. There is not much chance of bumping into an Egyptian, Israeli or American official at a local bar.

One of the few people allowed to roam Thurmont freely is Jerrold Schecter, the spokesman for the National Security Council. It fell to him late Wednesday afternoon to distribute a brief written statement that said nothing except that the first meeting of Carter, Sadat and Begin lasted one hour and 40 minutes and was held on a patio.

But when he appeared in the Legion hall auditorium, Schecter wasimmediately surrounded and hands clawed toward the scraps of paper in his hands.

"My God, they're like a pack of dogs," said one horrified woman.

Eventually, however, the summit will end and the two presidents and the prime minister will emerge and have something to say. In the meantime, the reporters can sit around the Legion hall named after a Thurmont boy killed in action in World War II and amuse each other with observations like this one from a seasoned veteran of these affairs.

"This is one of those situations," he said, "where the truth is obvious. They don't know what they're doing here."

Neither do we.