The H-2B worker program was designed to fill gaps in the labor force. In theory, as companies with a need for seasonal work grew, there would not be enough American citizens to fill the gaps. Businesses apply for "certified positions", or job vacancies approved by the Department of Labor that an immigrant holding an H-2B visa can fill. These businesses must show that "there are not enough U.S. workers who are able, willing, qualified, and available to do the temporary work" and that "employing H-2B workers will not adversely affect the wages and working conditions of similarly employed U.S. workers."