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There are other ways to use grids. Thumbnail sketches work really well in a grid format. Here's a "bus sketching" session:
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When sketching from the imagination rather than from life, using a closely spaced grid can stimulate creative thinking. Allowing lines from one grid box to flow into the next permits an uninterrupted flow of ideas. Not all of these thumbnails will be useful, but in this approach quantity comes first. Discerning the best image becomes a process of elimination.