Sketches serve to externalize ideas, to render fleeting ideas permanent, to confer coherence on scattered concepts, to turn internal thoughts public. They can be created and recreated, examined and reexamined, configured and reconfigured, considered and reconsidered, for clarity and for creativity. The schematic vocabulary of sketches allows both expression and discovery of ideas. Sketching is integral to design, where vagueness encourages reinterpretation and discourages fixation. Using sketches to those ends requires constructive perception, a combination of a perceptual skill of reconfiguring and a cognitive skill of finding remote associations. Why Sketch? Designers sketch. One reason they sketch is that they design things that can be seen. A sketch can resemble what the designer wants to create. A sketch can be seen, unlike the contents of the imagination. Thus, sketches serve to amplify a designer's imagination and relieve limited capacity working memory. Sketches map things in the world or the imagination and their spatial relations to elements and relations on paper, a natural mapping. They can convey large spaces by by spaces that are smaller, hence easier to contemplate. Models can do that as well, perhaps more so, as models are three-dimensional. But models have disadvantages over sketching, especially in the early stages of design, when the designer is considering many alternatives, and those alternatives may be vague or partial. Models demand completeness. Sketching is faster than building models, and is kinder to trial and error. Sketches are straightforward to create and straightforward to revise. Sketches are two-dimensional, thus easier to think about, as thinking in two dimensions is easier than thinking in three. Sketches readily enable isolating different parts, different perspectives, and different scales and working on them separately. A designer can use a sketch to focus on some aspects of the design, ignoring aspects that may be distracting or confusing. Sketches are visible. Because they are visible they can be inspected and reinspected, considered and reconsidered. As shall be seen, designers can discover new properties and relations from their sketches as they inspect them, properties and relations that emerge from the sketch but were not intentionally put there (e. g.
