The research deals with freehand sketching and diagramming techniques, explaining its important role as a design tool in early stages of architectural design process, as a tool of design thinking, a tool of communication, and a tool of interpretation and reasoning. In relation to its role as a tool of design thinking varying between conceptual and perceptual thinking, it is active in the initial stages of the design process, which are the exploration, extraction and development stages. It plays a prominent role in the exploration phase through stimulating and expanding designer thinking as an assistant tool in analytical thinking, retrospective thinking and speculative thinking. Its role in extraction phase as synthesis tool leads to investigation of alternatives, and as evaluation tool to test and verify the design solutions. In development phase, it helps the designer thought to reach the re-interpretation and unexpected discoveries. The research highlights freehand drawing techniques role as a communication tool between architect and himself, and architect and his group or architect and public. In addition to its role as interpretation and reasoning tool to reveal the designer intentions explaining the design content or design process.