Suppose that for family, medical or personal reasons you must make a mid-career move to another part of the country -- and you must have a good, steady job when you get there!

For many people, a forced move is a fact of life. And also a major problem. Most companies don't have offices nationwide. Moving, for many people, means a different employer. Often it means taking a pay cut, losing pension rights, vacation, sick leave and so forth. It can also mean starting over, at the bottom.

Unless you work for the U.S. Postal Service.

With 830,000 workers, the Postal Service is one of the nation's biggest employers. It is the largest federal agency. Clerks and letter carriers average about $29,000 in pay with an estimated fringe benefit package that is worth an additional $9,000 per year. Unlike most companies or federal agencies, the Postal Service is everywhere. And job-swapping is allowed.

Postal workers who know the ropes can trade locations with other workers. The clerk or letter carrier must clear it with the boss, and find somebody in another town or city who is willing to make the trade with his or her postmasters' approval.

One of the best-read features of magazines aimed at postal workers is the "trade" or "transfer request" sections. They work something like personal ads. But instead of a divorced 50-year-old man who likes cigars and duck-hunting in search of a like-minded woman, the postal ads may be from a rural carrier with a right-hand drive car and a 41-mile route seeking a similar situation across the country.

Clerks and letter carriers who can negotiate job swaps may keep their salaries, vacation and benefits. But their duties at the new location aren't guaranteed. Rural letter carriers, who are paid based on the length of their routes and boxes served, often look for somebody at their same pay level when seeking to swap.

Each month, hundreds of postal workers advertise swap situations. Some make the move as a pre-retirement step. Others want to be closer to (or farther away from) relatives, or to get near certain medical facilities or find a gentler climate.

Examples of some recent swap ads:

Sally Shields, a Manassas letter carrier, needs to move for family medical reasons. Her ad in the Postal Record magazine asked for a mutual transfer "to any office between Johnstown and State College," Pa.

Karl Oltmanns, of Sturgis, S.D., offered his "Black Hills, hunting, fishing, skiing, gambling, mountains" life for a trade to northern Wisconsin or Chicago.

John W. Huskey, of Laramie, Wyo., definitely wants a change of scene as he seeks a swap that will put him close to Las Vegas.

Clara Guzman, a Wall Street letter carrier, advertised to relocate "to anywhere in Northern New Mexico" if she can find someone eager to come to the Big Apple.

Some of the job swap proposals are specific, such as "want the northside of Chicago" or "must move to Alton, Illinois." Others seem, well, less so, such as the postal clerk in Puerto Rico who advertised that he would like to swap for a job "in either Miami, Florida, Anchorage, Alaska, or Williamsburg, Va."