A full-size preparatory drawing for a stained-glass window is called a cartoon. It serves as the working plan from which the artist and glaziers develop the finished window.
The cartoon normally shows the composition, figures, ornament, lead lines, and placement of individual pieces. In historical workshops, it could be drawn on paper, parchment, or a temporary surface large enough to match the intended window opening.
Once the design was approved, craftsmen used it to make templates for cutting the glass. Painted details, such as faces and folds of clothing, were also planned against this design. The cartoon helped coordinate the work of artists, glass painters, cutters, and lead workers.
The term is not related to modern animated cartoons, although both words ultimately concern drawn images. In stained-glass history, a cartoon is a serious architectural and artistic blueprint, not the colored glass itself.