The varying functions of physical engineering models within a design/development environment are explored and their significance in the progression and overall success of a project evaluated. Based largely on the author's first hand experience within industry, the function of a model as an ergonomic, engineering design, laboratory and field service performance vehicle is examined using case study material (a lawnmower design) to identify the practical aspects of these critical areas. The relationship between engineering models and industrial design models is also considered. The conclusions drawn are that the use of physical engineering models affords real benefits in terms of time scale progression by providing a strong focus on the state-of-the-art of a project. In addition, their psychological benefits in terms of being able to convey ideas rapidly, using a hands-on approach, to third parties concerned with design within an organisation e.g. Marketing, Production etc. cannot be understated. This is particularly true when they are used in conjunction with computer aided design and/or industrial design models.