Rocket Cleaners, a third-generation business, opened its doors in 1938 in Hyde Park. Today, all items dropped off at its Sharon-based store are sent to its large, on-site Hyde Park facility for cleaning. Rocket's clients include federal, state and city government offices, the military and universities. Its best kept secret: They clean costumes for Boston theaters, universities and the Boston Ballet. They use green cleaning techniques for every cotton and combination cotton garment. Seniors enjoy a 10 percent discount, which is offered every day.