The rings represent the dials of a combination lock. If you could rotate the eight rings you could create a large X-shape in one colour across the afghan. This is a difficult visualisation problem. Scroll down for a solution. There are 128 ways to form the X.
Crocheted entirely in treble crochet (UK terminology). It is made in one piece and only one yarn is used at a time. It may look like a circle but it is really a 24-sided shape. NOTE: A pdf version of the pattern is available but there is no printed version.
The afghan in the photo was made using DK yarns. You can use other yarns though this may cause your afghan to be bigger or smaller. The pattern includes other suggestions for changing the overall size of the afghan. Six distinctly different colours are needed. They do not have to be as bright as those in the picture. It is best if they are all of the same intensity so that no one colour is dominant and could cause confusion.