At Hechinger Co., home of do-it-yourself, the executives practice what they preach. With all the enthusiasm of Harry Homeowner constructing a garden wall with Hechinger bricks, the company's leaders have steadily built up the value of their company's stock by issuing regular stock dividends.

Eight times in seven years, the company has approved the payment of additional shares of stock. The most recent is a 5-for-4 split, payable June 17 to shareholders of record June 7. The effect of the dividends, coupled with the rising price of Hechinger shares, has been dramatic -- although it should be noted that it took many years for shareholders to realize their gains.

The investor who bought 100 shares of Hechinger when the company went public in 1972 at $16 a share -- and thereby invested $1,600 -- would today have 647 shares worth about $22.50 a share, or $14,558. That's an increase of 810 percent, or 62.3 percent a year. The $22.50 figure is the expected price of Hechinger stock after the new split.

The stock dividends began in August 1978. The first was a 4 percent dividend. After that they went this way: August 1979 (20 percent); May 1980 (20 percent); May 1981 (3-for-2 split); September 1982 (5 for 4); January 1983 (3 for 2) and June 1984 (5 for 4).

This list does not include the stock dividend granted in October 1983 as the result of Hechinger's move from a single class of common stock to two classes, A and B. All existing shares then were designated as class B shares and each stockholder got one new A share for every four old B shares. Thus, if a shareholder held 100 shares of original Hechinger stock, he was given an additional 25 shares of new class A stock.

Stockholders also were given the right to convert class B shares to class A shares if they wished. The class A stock had one vote per share instead of the 10 votes per share that went with class B shares. But the class A had a higher dividend. Class A now pays 16 cents a share while class B pays only 8 cents a share.

Hechinger Co. began life in 1911, when Sidney Hechinger started a wrecking business, salvaging building materials and reselling them. When he discovered he could sell new building materials more easily, he opened his first store in 1919. When he died in 1958, he had seven stores but he had told his children that someday Hechinger would be "another Sears, Roebuck."

Today, 27 years later, the Hechinger Co. operates 47 stores and has moved outward from the District, Maryland and Virginia into North Carolina, Ohio, Pennsylvania and New York. Operations in other states, including New Jersey, South Carolina and Delaware, seem sure to follow as John W. Hechinger launches a new expansion drive, with a goal of adding 28 stores in the next two years.

Hechinger Co. still is very much a family operation. John W. Hechinger, Sidney Hechinger's son, is the president. His brother-in-law Richard England is the chairman. John's sons, John W. Hechinger Jr. and S. Ross Hechinger, are active in the business. So is Richard England's daughter, Joan S. England.

The Hechinger and England families have substantial control over the business, owning almost 2 million shares of class A stock (about 27.6 percent) and 8 million shares of class B stock (73.4 percent).

One of the stockholders who attended last week's annual meeting expressed concern about the rapid pace of expansion planned for Hechinger. John W. Hechinger said he was aware of the concern but believed the company had the funds, the leadership and the expertise to make it work.

"There is some risk in aggressive expansion," noted one close observer of the Hechinger operation. "But the company has been balancing its expansion between old areas and new areas . . . and that tends to decrease the risk."

Hechinger, for instance, has added stores this year in new areas, including Columbus, Ohio, and Greensboro, N.C., and has selected sites in Rochester, N.Y. But it is also adding additional stores in proven areas, including Philadelphia, Baltimore and Washington.

Hechinger has set a torrid pace for itself, racking up 41 consecutive quarters of earnings increases as part of a pattern of steady growth of sales and profits that has produced a five-year annual growth rate of 70 percent. At $27 a share, the pre-split price, the stock is selling at 23.5 times its 1984 earnings of $1.15 a share. That is somewhat rich for the industry but reflects the powerful growth trends in the home-center business and the aggressive expansion drive by Hechinger.

It is those factors that have helped propel Hechinger stock from about $16 a share a year ago to about $27 a share currently, a rise of 68.8 percent.

If the Hechinger people can maintain the pace of their sales and profit growth, the value of their stock is likely to grow along with it.

On the Move: Here are some of the Washington-area stocks that have been reaching new highs in recent weeks and their percentage of increase since Jan. 1:

American Furniture of Martinsville, Va., up 40 percent. AVEMCO, a Frederick, Md., insurance company, up 52 percent. BDM International, a McLean professional services company, up 55 percent. Dibrell Bros., a Danville, Va., tobacco company, up 41 percent. Equitable Bancorp, up 60 percent. Ethyl Corp. of Richmond, in energy and chemicals businesses, up 35 percent. Figgie International Holdings of Williamsburg, Va., up 52 percent. First Virginia Banks, up 30 percent. Geico, a District-based insurance company, up 31 percent. General Physics, a Columbia, Md., professional services company, up 40 percent. Giant Food, up 37 percent. Heilig Meyers Co. of Richmond, a furniture retailer, up 50 percent. Legg Mason, a Baltimore brokerage house, up 57 percent. Manor Care, a Silver Spring nursing home company, up 50 percent.

Martin Marietta, the Bethesda aerospace company, up 30 percent. Owens & Minor, a Richmond hospital supply company, up 76 percent. The Rouse Co., the Columbia, Md., development company, up 36 percent. Verdix Corp., a McLean computer company, up 292 percent. The Washington Post (B), up 59 percent. Waverly Press, a Baltimore printing firm, up 49 percent.

The American Association of Individual Investors (AAII) has developed what it calls the "Shadow 440," a list of small, promising companies that generally escape the Wall Street spotlight. The companies have three things in common: The market value of their stock is between $20 million and $100 million; they are established industrial firms with at least two years of positive earnings; and their stock is held by few institutions and they are not covered by many investment analysts.

Washington-region companies appearing on the list include: American Filtrona, American Furniture, Computer Data Systems, Computer Entry Systems, Fair Lanes Inc., General Physics, Kay Corp., Legg Mason, Noland Co., Penril Corp., Pulaski Furniture and Scope Industries.

Shadow stocks are appropriate, said the AAII, for investors who have a portfolio of 10 to 20 stocks or hold shares in diversified mutual funds and who will not need their assets for at least five years. The longer holding period helps lower the investment risk, the AAII said.