President Bush's signature on the Americans with Disabilities Act forces businesses to look at two kinds of barriers that handicapped people face -- physical ones like stairs and narrow doorways, and less visible obstacles like hiring practices.

All businesses, small and large, that are open to the public will eventually have to do something about public accommodations under the law, and companies with 15 or more employees will be subject to its job discrimination provisions.

Among many small firms that have no formal policies regarding the disabled, there is confusion about what they will be required to do, and some are particularly upset by the public accommodation rules, which they see as just another burden to small business.

Barbara Balter, president of Robert B. Balter Co. in Owings Mills, Md., said she hasn't read the law, but is angry just the same. She said her environmental technology and engineering consulting firm, with nearly 100 employees, will have to install wheelchair ramps, elevators and telephone devices for the hearing-impaired, all by the law's summer 1992 deadline.

"Who's going to pay for it?" she said. "You can't pay for these things and meet expenses if times are slow."

But the part of the law that affects the greatest number of businesses -- the provisions covering hiring practices -- will not cost them anything, said John Santagaj, president of the Small Business Legislative Council, a coalition of trade groups with small-business members.

Businesses will have to rethink the way they interview job applicants, whether the questions they ask are relevant, Santagaj said.

"They'll have to put a little more thought into the upfront process," he said.

That's not a matter of cost, he stressed, but "of discipline. For a small business it's a little more difficult to get that discipline in the process."

Part of that process involves writing job descriptions, something new to many small businesses where job descriptions change as the company does and personnel specialists are nonexistent, Santagaj said.

Barbara Judy, a project manager at the Job Accommodation Network, based at the University of West Virginia, said she advises companies to break down the essential and unessential parts of each job description.

"I tell them to itemize all the things that that person did -- break down each action ... to see who can do what," she said.

Employers can face a lawsuit for turning down an applicant who can perform all the essential parts of a job, but, because of a disability, can't perform an unessential duty traditionally included in that job description.

While most business owners don't see major costs in changing their hiring policies, many, like Balter, see red when they hear about the public accommodation requirements. However, advocates for the disabled and even the small-business lobby groups that opposed the legislation say such work won't be prohibitively expensive if executives do not panic.

Companies with 25 or more employees will have two years to comply with the law, and those with 15 to 24 employees have another two years after that to outfit their businesses with ramps, elevators and other devices for disabled employees. All businesses that host the public -- such as restaurants and stores -- have to comply by 1991.

The law requires work on making public places accessible to the handicapped to be "easily accomplishable and able to be carried out without much difficulty or expense." In addition, House Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.) last week introduced legislation that would give a construction tax credit of as much as $5,000 for companies with fewer than 15 employees and less than $1 million in annual sales.

To alleviate some confusion, the local office of the Small Business Administration is planning to hold seminars outlining the law's guidelines in the fall. Local offices of National Small Business United also are planning seminars.

Creativity isn't ruled out either, Santagaj said. "For most small businesses, we're hopeful that they can address the needs of their disabled customer base by using alternative methods rather than structural changes," he said. One oft-cited example is that of the dry cleaner coming to the door of his shop to serve disabled patrons if widening the door would be too costly.

Jack Kaeufer, president of Foot Management Inc., a small manufacturer of orthotics in Salisbury, Md., has sought to employ disabled people since he started his company 16 years ago after a back injury ended his steamfitting career.

The cost of altering his building for employees whose disabilities included deafness, epilepsy and a bad back was minimal, he said. It included raising and lowering work surfaces and widening doorways. When he had a new building constructed, making it more accessible to the disabled cost added just pennies to the cost, he said.

Nor does the performance of disabled employees hurt the company, Kaeufer said.

"We hire all the way around the bush," Kaeufer said. "But we do lean toward the disabled individual -- because they've proved themselves. They're so appreciative in that employment that they give that little bit extra that makes a good employee."