In the managerial world Elliot Jaques is quite well known for this theory of Requisite Organization. His work Level of work concept has has a lot of benefit and merit. Jaques Levels of Work model has practical application for managers seeking to understand and work with organizational complexities, especially in organizations undergoing change. Though the theory is quite a complex one, but it can be put in simple terms in this manner. If you want to really put it in use you will have to do some more research and gain more knowledge. This theory is highly applicable for technical jobs to ascertain the right candidate for a technical task.
Back in the 1950's, while searching for a reliable method for assigning differential pay to roles with varying degrees of responsibility, Jaques discovered the Time-Span of Discretion. In one of his latest books (A Theory on the Life and Behavior of Living) he called this "the greatest discovery in my life". This method makes it possible to measure the level-of-work of any given work role with objective rigour.