The TWI trainers had to be invited to a factory in order to present their material. In order to market the service, they developed the Five Needs of the Supervisor: every supervisor needs to have Knowledge of the Work, Knowledge of Responsibility, Skill in Instructing, Skill in Improving Methods, and Skill in Leading.[2] Each program was based on Charles Allen's 4-point method of Preparation, Presentation, Application, and Testing.