Celtic knots

To artists and mathematicians, knots can be beautiful, interesting structures. Until recently, I hadn't explored them much from either perspective. Then my mother-in-law gave me a copy of George Bain's Celtic Art: The Methods of Construction for my birthday Bain shows how to create Celtic knots, from simple to elaborate.

Let's make one, partly based on Bain's techniques. Celtic knots can be used to fill complex shapes, but many of the motifs fill rectangles, and this is a good place to start. You may want graph paper, pencil, and an eraser. Create a grid with an even length on each side. I'm using 8x6 here, and you'll notice that I have accented every other line, so that there is a 4x3 grid of 2x2 cells.