The picket fence There was a fence with spaces you could look through if you wanted to. An architect who saw this thing stood there one summer evening. Took out the spaces with great care and built a castle in the air. The fence was utterly dumbfounded, each post stood there with nothing round it. Christian Morgenstern, The Art of Looking Sideways www.andrew.cmu.edu spacearchitectureabsurdity
Truchet Tiles Truchet tiles are square tiles decorated with patterns that are not rotationally symmetric. When placed in a square tiling of the plane, they can form varied patterns, and the orientation of each tile can be used to visualize information associated with the tile's position within the tiling. Wikipedia en.wikipedia.org The Tiling Patterns of Sebastien Truchet and the Topology of Structural HierarchyWang tiles graphicsart