Every workday, hundreds of Americans send copies of their work--from manuscripts to macrame' kits--to the U.S. Copyright Office.

"People want protection for letters, toys, songs, gags, you name it," says Victor Marton, supervisor of the copyright-information office. "We hear from musicians, writers, bookkeepers, plumbers--the whole gamut of America. They call us, write us or walk in off the street.

"One day last year Red Skelton came in to check on some of his art work, and we got a call from Marlene Dietrich in Paris. We had one gentleman come in who'd been working for 30 years on a manuscript about World War II and wanted to personally put it in our hands."

What most people are seeking, he says, "is peace of mind. People today are very concerned about getting ripped off--not just their bicycles and property, but the products of their mind."

When the long-awaited revision of the 1909 Copyright Act went into effect four years ago, federal officials expected copyright registrations to decrease. Since the new law provided automatic protection upon creation of a work--and raised the registration fee from $6 to $10--they assumed fewer people would exercise the option to register their work.

"But it didn't happen that way," says Marton. "Registrations went up a little at first, and have been rising steadily since then." In 1981, copyright registrations reached an all-time high of 471,178--more than 1,800 per workday--up from 429,004 in 1979.

As a writers' mecca, Washington is a "particularly busy town in terms of copyright," says attorney Ronald Goldfarb, who has more than 200 writer clients and offers group legal services to the 1,400 members of Washington Independent Writers (WIW).

"This town is full of people with good ideas . . . it's the center of the nonfiction world, and there's a tremendous amount of fiction written here, too."

Possibly because "writing tends to be an extracurricular thing," Goldfarb says, "it's growing fantastically. WIW gets about 50 new members each month. You've got your lawyers writing the definitive anti-trust book, your trade association PR executives who hunger to write Rablais-style poetry, your hausfraus writing the Great American Novel."

But despite the large number of writers, notes Michael S. Keplinger, chief of the copyright office's information and referral division, "there are some popular misconceptions" about how the copyright law works.

"A lot of people think we issue copyrights the way the patent office issues patents. But that's not so. The law gives you the right to put the copyright symbol on anything published or unpublished. You don't need special permission from us to do so."

Confusion often arises, because the old law required "publication with notice of copyright" as a condition of protection. But under the 1976 act (which went into effect Jan. 1, 1978), copyright is secured automatically when the work is created in fixed form--such as on paper, videotape or film.

Copyright immediately belongs to the author, says Keplinger, "unless it is work prepared by an employe within the scope of his or her employment, or work specially ordered or commissioned." This "work-for-hire" provision, he notes, is of particular concern to free-lance writers and artists. Generally, the free-lancer sells copyright only for the "use with which it was intended."

While registration is "a legal formality" and not a condition of copyright protection, "it does provide certain advantages," says Keplinger. "If you do encounter a problem with infringement, your certificate of registration can be your ticket to court."

Since registration establishes a public record of the copyright claim, it is ordinarily necessary before any legal suits may be filed. Registration can establish the validity of the copyright and, in some circumstances, win the copyright owner statutory damages and attorney's fees.

The incidence of copyright infringement is difficult to determine "since so many cases are settled out of court," says Keplinger. While the copyright office takes no stand on whether or not a work should be registered, he says, "Personally, I think it depends on the work. One should consider whether it has commercial value.

"If I were writing a book to submit to publishers I'd register. If I were in the business of writing computer programs I'd probably register. If I were a casual author, maybe not."

Registration also may result in the work's inclusion in the Library of Congress' collections. Twice daily, a Library of Congress employe reviews material submitted for copyright registration. Items not selected--usually unpublished works (except genealogical records), "vanity-press" publications, most elementary and secondary school textbooks--are stored in a Landover, Md. warehouse "which is now virtually full," says Keplinger.

The copyright office, he says, "reads just enough" of a work "to determine if it is copyrightable." They do not check to see if the submission is similar to work already registered, but will search copyright records for a $10-per-hour fee.

One of the most frequently asked--and toughest--questions is "What is copyrightable and what isn't?" (See box below.) As a rule of thumb, says Keplinger, "Ideas cannot be copyrighted, but the expression of that idea can. The basic tension in the law is the question, 'Where does an idea end, and the expression of that idea begin?'

"Video games are a good example of this. There are a lot of cases going on now with names like Meteors vs. Asteroids, where the central question is whether they're using the idea or the form of expression. Generally, originators of a game have been very successful in getting competitors taken off the market."

Other controversial copyright areas: cable TV, video cassette recordings, computer programs and use of copy machines. Currently, the copyright office is studying the use of library photocopy machines and will submit a report to Congress in 1983 on whether their operation constitutes "fair use" of material.

It's difficult, Keplinger admits, "to keep up with all the copyright ramifications of new technology. Basically, the law tries to give creators the reward due them for their contribution to society."