The Ryland Group, Inc., of Columbia has elected Robert J. Gaw president and chief operating officer.

Past president James P. Ryan will continue to serve as chairman of the board anc chief executive officer.

According to the announcement, Ryan will concentrate on long-term planning and policy formulation while Gaw will be responsible for the daily operation of one of the country's largest builders of single family houses.

Gaw, one of the founders of The Ryland Group, has been executive vice president of the company for the past three years. Prior to that, he was vice president for finance and area manager of the company's Baltimore and Washington operations.

Bank of Virginia Co. announced that Donald R. Just has been named president of Bank of Virginia-Potomac. On July 1, he will replace Malcolm S. McDonald, who is transferring to the parent company's Richmond headquarters as a senior vice president.

Just, who will also be in charge of all Bank of Virginia's operations in the northern region, is currently president of the chief executive officer of Bank of Virginia International, a subsidiary of the parent company.

Succeeding Just at Bank of Virginia International is Julian W. Banton. Banton has been an executive vice president with responsibility for the commercial division at Bank of Virginia.

Union Trust Co. of Maryland has appointed Margie H. Muller vice president for marketing.

Muller joins Union Trust after six years with Maryland National Bank where she was vice president for public relations. Prior to that, she was an assistant vice president for marketing at Tomkins County Trust Co. of Ithaca, N.Y.

George Hyman Construction Co. has named retired Rear Admiral Albert R. Marschall vice president. Marschall held the top command post of the Civil Engineer Corps and was responsible for construction operations in support of U.S. Navy operations world-wide.

Woodward & Lothrop has appointed Robert E. Friedman vice president and general merchandise manager. He comes to Woodies from the May Co., where he was vice president and general merchandise manager for ready-to-wear in Cleveland.

Pubco Corp. has named Martin L. Fleming vice president and treasurer. He will also serve as treasurer of the Glan Dale-based company's wholly-owned subsidiaries. Byron S. Adams Printing Inc., Buxton & Skinner Printing Co., The Publishers Agency, Inc., Redson Rice Corp. and The Tabard Press Corp.

Robert E. Anderson has been appointed vice president for marketing of Black & Decker's professional products division. Anderson has been with Black & Decker since 1970, when he joined the company as a general sales manager.

Robert E. Ruckle was been elected vice president of John Hanson Savings and Loan, Inc., of Forestville, Md. He has been, for the past 15 years, with the Savings and Loan Associations of the State of Maryland.

Maryland National Corp. has named Hugh A. Woltzen vice president and division manager of the company's new credit services division. The new division will perform the credit function for the company's non-bank subsidiaries. Woltzen was vice president in the commercial banking division of Maryland National Bank, a subsidiary of Maryland National Corp.

Also named a vice president in the division was Duncan A. MacRae, formerly vice president and senior credit officer of Maryland National Industrial Finance Corp.