A piano key border is simply strips sewn together and then cut into whatever size you want. For example, if you sew 2 strips that are 2.5" wide and the WOF (width of fabric), then sub cut those into 4.5", you can then sew those blocks together and you would have alternating stripes of those two colors, and your finished border would be 4 inches wide. I like to sew a variety of pairs to get in more fabrics. This is also a great way to use up short scraps.Originally Posted by saf
You could just as easily sub-cut your strips 6", 8 inches, whatever.