If you want to work only occasionally, or need to sandwich jobs into short periods of free time, sign up with an agency that specializes in temporary help. Jobs for temporaries are booming. In many parts of the country, there are more openings than the agencies can fill. In Washington for example, it's estimated that 150 to 250 temporary jobs go begging every week.

Temporary work schedules are ideal for housewives, students on vacation, teachers during holidays, new arrivals in town trying to get a feel for the job market, and the unemployed waiting for job interviews. If you're seeking full-time work, a temporary job may get you in the door. This type of employment can also be helpful to older housewives, trying to decide whether to return to the work force.

Behind the big demand for temporary workers lie a couple of important economic trends.

First, the labor market for experienced and skilled workers has grown tight as a drum. Although the official unemployment count remains high, the core work-force is probably about as fully employed as it ever was in boom times. Companies can reach only so far in to the unskilled labor for clerical workers and data processors. A good portion of the unemployed simply aren't employable in the work available.

Second, many companies - large and small - have moved to Sunbelt and suburban areas, where workers are in short supply. Skilled engineers may be easier to get than skilled stenographers. Companies in the Stamford, Conn., area face this kind of problem. Ted Youngling of The Connecticut Temporaries says they're dependent on the "mature woman" to fill the job gap.

Third, when the job market gets this tight, it's often the economic upturn's last hurrah. If we should slide into slower growth or recession next year, it's easier and less expensive to cut back on temporaries than on full-time personnel.

There's yet another another reason for the growth in temporaries, that companies talk less about. Many businesses have "had it" with pension fund contributions, unemployment funds, state disability funds, minority hiring rules, and all the other "ills" a personnel department is heir to. There are no government regulations regarding temporary help.

"Once in a while we get a strange job, like the company that wanted 100 people to test the strength of a rope in a tug of war contest," Charles Deale, spokesman for the National Association for Temporary Service in Washington, told my associate, Anne Colamosca. "But our stock in trade is still skilled clerical help. Our biggest demand is for people who can type, take shorthand and do data processing."

Deale says that more men are getting temporary office work, and are much welcomed. Overall, 70 percent industrial, and 10 percent tug-of-war and others.

Demand for temporaries is so strong that some agencies have taken to advertising wage rates in the newspapers. This has caused some disension in the industry, but hasn't appeared to have raised wages too much. Clericals earn from $2.50 to $7 an hour, depending on skills. The average mark-up for the agency is 40 percent or more over that.

Staff Builders, a New York-based agency with 72 offices nationwide, specializes in supplying temporary health workers. In New York, much of the work is home health care for the ill and aged. In other states, especially where unions are weak or non-existent, temporaries are much used in hospitals. Registered nurses, get close to $6 an hour (Staff Builders makes another $4), the practical nurses, around $4.50.

Incidentally, people who work the required period of time for a temporary help agency can file for undown for a job. But the way demand is running, turndowns are rare. One woman, an unemployed photographer who signed up with an agency, says she is called constantly for clerical jobs, even though she can't type.