It was time for yet another Panamanian national fiesta as massive crowds turned up to watch President Carter and Gen. Omar Torrijos in a downtown plaza of the capital. They appeared side by side on a white platform under a giant, almost mystical sign: a ship, crowned with a halo, moving into the opening locks of the Panama Canal.

It was Panama's fourth national holiday in 10 months to celebrate different stages of the protracted Panama Canal treaty talks. The first came last August when the agreements were initialed, and another in September when Torrijos brought the signed documents back from Washington. A third was announed when the U.S. Senate finally ratified the documents in April.

But for yesterday's exchange of ratification documents, billed here as "national liberation day," the government was determined to put up the best possible show.

There were banners and music as tens of thousands of people packed Fifth of May Plaza, spilling into side streets full of stores jammed with panama's tax-free goods.

All day trucks with traveling bands had been playing the "Pindin" and the "Trambolera," panama's cheerful fast rhythm's, to help people forget the tedium of the long, hot hours they had to wait for Carter. Panamanians like a party and many don't care about the politics attached to it.

They had come from Panama's nine provinces, peasants from Chiriqui in the West and from the jungles near the eastern border with Colombia. Though they had heard something about the appearance of Carter and Torrijos, many of these country folk had little idea what the mass meeting was all about.

"I came to find out about this place" said a Gaymi Indian from San Feli de Tole, who had walked two hours and then traveled eight hours by bus.

"The government gave us buses. I came because I've never been here before." There were 30 buses from Volcan in western Panama whose passengers had traveled since three in the morning. Some of them said they came because "Torrijos told us to come."

It was a huge, festive motley gathering of Indians who could speak only their native tongue but were holding up pro-government sign in Spanish, and of Politically conscious urbanites from the capital and from Colon.

A teacher who said she came because she had "heard so much about Jimmy Carter I'd like to see him with my own eyes" stood next to an opponent of the treaties who said he was here "because today is a piece of our history."

Panama's leader, Gen. Torrijos, spent most of the morning at Tocumen airport receiving the few civilian presidents remaining on the American continent. He is a general who came to power in a 1968 military coup.