Stair diagrams are a great way to show the process of a given product or service. A stair diagram is an illustration that shows how something is done, step by step. They are often used in business presentations to show how a process works or in education to illustrate the steps of a scientific experiment. The stairs represent the stages of the process and they are usually numbered from 1 to 5 with each level representing one stage of the process. The top level (level 5) represents completion and success.