The checkerboard pattern has served as the classic ACL 4 design for decades, because it is found in the folk art of cultures all around the world and the distinction between ACL 4.2 and 4.4 is so clear.
Within ACL 4.2, people can alternate colours just fine along the first row, but the second row creates problems. In the second row, one must alternate colours horizontally and vertically. The second row can be done correctly within ACL 4.4. Within ACL 4.2, the checkerboard pattern is often replaced by vertical stripes.
Horizontal and vertical lines and rows use two-dimensional space. The third dimension is added to the scale within ACL 5.4. Within ACL 4.4, the grid around the border of the notecard compensates for their difficulties with spacing.
