Design in its fullest meaning is the top role of the engineer (Hrones, 1960). Before any work of human skill can be produced it must be imagined. In essence, it is this human power of imagining something that did not exist before that is termed "design" (Harvey, 1950). This chapter is therefore concerned with an outline of the knowledge, skill and imagination required by the designing engineer; the progress of a new piece of equipment (in the abstract) is traced from the original idea up to the point of production; the probable approaches adopted by designers in solving engineering problems are indicated, and the use of various "tricks of the trade" to help in this process; finally where these tricks are useful in the context of a small selection of technologies is shown.