What country are you in?
American style Rumba (or Rhumba) is based on the box. International style isn't. (Or maybe it is. Another way of looking at it: One of our local instructors talks about the "Latin box," created by taking a standard box, cutting it in half along a diagonal, and moving one half above the other half. This "box" is used in Mambo, Cha-Cha--with the obvious modification--, Bolero, and International Rumba.)
If you live in the United States, look for a 10-minute movie that occasionally appears on Turner Classic Movies, called "Cuban Rhythm." This movie, from 1941 (http://www.imdb.com/title/tt0033503/), features Arthur Murray instructors teaching the Rumba--using the box. Styles have changed somewhat, but it's still fun to watch.