Federal and postal labor unions - representing more than half the government work force - come into this Labor Day much like an adolescent at his or her first big dance or date. They are at the point where nothing big may happen right away, but even so they will never again be the same.

Before you decide this section of the paper might make a nice carpet for the birdcage, be advised this isn't going to be THAT sort of Labor Day message. You will be getting the other kind from dawn to dusk.

Today, all day, those of us who are not at the bottom of some cave will be bombarded by messages about Labor Day. High officials who normally could care less about labor will lay wreaths at the Tomb of the Unkown Shop Steward.

High church leaders, who wouldn't know a worker if they blessed one, will praise the people with callouses on their hands. Politicians will extoll the people who make cars and cut up cows for the rest of us. Business leaders will praise the workers who, the other 364 days a year, they are trying to pay the least amount of money possible until they can find a machine to replace them all.

And Labor leaders, perhaps the dullest people of all on Labor Day, will tell members how good things are (thanks to them, the labor leaders) but warn the faithful (lest they turn in their dues checkoff cards and retire to paradise) of new threats for working persons, of new attacks on the horizon, and new dangers that require everybody to keep together and keep returning the same labor leaders to their jobs.

Today is the day for lots of talk. It will range from the sugar-coated, up-with-labor type of inspirational message to the harsh warnings designed to keep the dues-payers' adrenlin flowing.

For government unions, this genuinely is a turning point. The big organizations that take in millions of dollars but never finance a strike are going to have to become more like unions, or return to being the sororities and fraternities of the bureaucracy.

Virtually all of the unions have broken with the White House. The same groups earlier had broken with Nixon and Ford. But that was understandable. They were known anti-union Republicans. The kind of guys who spent days like this at golf courses or mountain retreats, not at labor picnics.

Both Nixon and Ford shaved the amount of federal pay raises (although Nixon did create a blue collar pay system that gives most U.S. workers an 8 percent to 12 percent pay edge on their industry counterparts). But that was expected. They were antiunion, every labor leader knows that.

Carter, however, rode in on the union vote - so the unions believe.He promised full pay raises for white collar federal workers, praised their blue collar counterparts, and signed a postal reform pledge written for him by postal unions. The leaders of all those unions have since called him a "liar" and worse, and all of them are threatening to tell people to get sick, go slow on the job or strike. The clock, as everybody knows, is already ticking in the U.S. Postal Service.

In their march toward militancy, the unions have a number of problems. None (but in the postal sector) has ever pulled off a strike, or even tried very hard. They have no experience in striking, no strike funds and only one-sided view of the outcome of a strike. Many of the militants think THEY hold all the cards. They have never heard of lockouts in which heartless employers bar the doors until strikers, one by one or collectively, beg to return to their lathes, spinning machines or in-boxes.

The employer-target of the government unions is not defined, making it tougher to decide whom one is striking against. Is it the President? Congress? Agency head? or the public? The product isn't cars or coal, it is service. Some Americans believe, right or wrong, they could get by without some of those services.

Today is an important Labor Day for federal and postal unions, for the people they represent (and don't represent) and for the American people who ultimately feel and foot the bill for what happens or does not happen in the government.

Is it worth risking more public ill-will by delaying mailing of Social Security checks to protest a 5.5 percent raise? Are postal union members playing bad poker, trying to increase a 19.5 percent, three-year pay package while risking their no-layoff clause? What if the people at the General Service Administration, or the National Archieves, went on strike and nobody noticed?What then?