Williamsburg, Va. — For one brief moment in its five days, the Williamsburg summit meeting was frozen. Security forces blocked off exits, closed the billowing food pavilion outside.
As millions of people in America and abroad watched, President Reagan mounted the mahogany dais at the College of William and Mary sports center Monday with the other delegation heads. He read the summit declaration.
Immediately afterward, Mr. Reagan was whisked away. Then the real Williamsburg summit resumed.
Summits are more bedlam than solemn pronouncements - teeming bazaars of official briefings and corridor huddles as several thousand journalists and aides-de-camp trade impressions and information.
Williamsburg was no exception. Distilled from the analysis of delegation leaders were these findings of progress here, and the outlook for next year's summit in London:
* The Reagan administration's staging, logistics, and agenda control of the Williamsburg parley were masterly, delegations said. The United States apparently learned from last year's bitter dispute at Versailles not to press too hard on sensitive areas like East-West trade. Reagan himself led private discussions, took notes, and guided his delegation's negotiations, provoking complimentary rather than derisive comments on his performance.
* The US gave no significant ground on security or economic matters. ''The Williamsburg parley largely endorsed the policy status quo,'' one foreign official said. The US gave ground only at the margins, or in ways that allowed both sides to claim satisfaction on contended issues.
* Reservations and second thoughts, however, quickly emerged after the security and economic declarations became public. The Japanese were concerned that Prime Minister Yasuhiro Nakasone might have ''gone beyond the consensus'' at home in supporting the summit's statement on Western arms talks with the Soviets.
The West Germans said they were more convinced than ever, after meeting with Reagan and his advisers, that there would be no change in US deficit policy, and thought US interest rates would likely rise later this year.
The French were pleased to escape with no major flare-ups with the US. They won inclusion of language in the declaration on exchange-rate intervention and a possible future monetary conference. They hoped the French public would not hear US interpretations, which played down their significance.
* But overall, the leaders found enough areas of agreement, enough chance for direct exchange, enough opportunity to emphasize broad policy concerns and objectives, to call the summit useful - if not an outright success.
Other leaders shared Reagan's hope that a less rehearsed summit, while posing greater risks for disagreement, could produce a more direct sharing of views.
''We have been banking the past several summits for a summit where there would be no proclamation of the leader in advance,'' said Canadian Prime Minister Pierre Trudeau. ''Unstructured, without a precise agenda, and, most important, without a lengthy communique which had been written over the period of weeks and months by our 'Sherpas' - that we would be meeting at summit level to, kind of, justify that we covered all these subjects.''
''I like meetings where you can argue and say, 'Where did you get this' and 'I don't agree with that' and so on, which was becoming increasingly difficult, '' Mr. Trudeau said. ''In this sense, I think President Reagan was taking a very big gamble that we could have an unstructured summit and still produce results.''
Actually, the leaders came with tentative texts and wordings on positions to assist in the bargaining.
Typical of leaders leaving Williamsburg Tuesday, Trudeau departed on a positive note. ''We came to Williamsburg determined to deal with two very important subjects,'' he said. ''The first was disarmament and the second was the economic situation. Without any exaggeration, I think that the Canadian delegation can say that we are very happy with the outcome on both those subjects.''
Just before leaving Williamsburg, Reagan told reporters, ''We stayed until we'd worked out what we all felt was a way to go on the particular subject. And there was no vote taken. There were no winners or losers. Before we settled on it (individual subjects), all seven were in agreement.''