"Two bells" was the name Mary Ellen Hopkins gave it when you saw that a design or block or other trick in quilting that could make your quilt even more interesting; more than just setting it with the same block repeated over and over or set it together with sashings. (I don't think she ever made a quilt that was sashed?!) She meant that a single block did not have to be the 'finished' idea for a quilt.....use it as the vehicle to make the design even better.
These below were 'borrowed' from Quilterscache.com, put into the Paint program on my computer and merely rotated different ways. You could do the same with photocopies.
Jan in VA