A chain happens when two single lines undulating in opposite directions collide. Because they add a more interesting element than simple lines, I use chains in many of my designs.
FOR SIMPLICITY OF USE, CONSIDER THE TOP ROW TO BE HEDDLED THREADS AND THE BOTTOM ROW TO BE OPEN THREADS ON ALL OF THE DRAFTS.
A chain can make a great focal point in the center of a pattern.
Here are a few different placements.