1 FAST provides a systematic approach to assure correct basic function identification. It graphically and visually displays each sub-function, supporting function, critical-path function and basic function. It provides for identification of high-cost areas. A FAST diagram may appear similar to a PERT network and a work simplification flowchart. However, FAST is function-oriented and not time- or operation-oriented. A critical path of all functions required to make the product/service work or sell is one result of a FAST diagram. FAST presents a Christmas-tree breakdown of all functions involved. The tree is visualized as lying in the horizontal position. The apex shows the basic function, the trunk shows the critical-path function, and the limbs or branches show the secondary and aesthetic functions connected to the critical path. The roots of the tree can be visualized as the reason for being of the study.