This document discusses the use and purpose of diagrams in architecture. It provides quotes and thoughts from several architects on how diagrams can represent threshold moments in design, focus on general ideas and concepts, and clarify and explain design intentions. Diagrams are described as being between a concept and a plan, using simple lines to visualize and convey an idea or understanding in a suggestive manner. They can be used to develop, explain, or transform thinking about a design or building project.