Graffiti artists often work on a piece in sketchbooks before they actually begin painting it. The sketchbooks sometimes use a grid to help plan out the design. Sometimes they go beyond planning, and create visual effects that look as if they were stretching or folding the grid. In the picture on the right, you can see someone who actually shows the folded grid, although this is rare. More commonly, you might see graffiti writers use the actual brickwork as a grid itself, as we can see in this picture below.

Whether it's a grid in a sketchbook, or a grid of bricks on a wall, these grids are much like the Cartesian coordinate system in mathematics. Let's see how we can map the Graffiti artist's grid onto the Cartesian coordinate system.