This doesn’t pertain to fitting, but one thing you may want to do is add at least one small border past the piano key border , to keep the ends of the piano key seams from coming open during quilting.

I haven't tried a piano key border but what about measuring the sides of the quilt then make two border strips about an inch smaller than half the length of the side of the quilt. Then cut a square for the center of the border strip the right size so that when you sew the border strips to each side of the square it 's the exact right length. Don't know if I'm being clear. In other words sew an odd size piece in the center of each strip on all 4 sides to enable the strips to be the correct size!? Might even want to make the 4 odd size pieces the same color to serve as accents.

I have made a bunch of piano key borders. I use different size strips, sewn together. After I pin to my quilt I just cut off the strips I don't need. Works right for me. I don't measure borders either, except down and across the middle of my quilt. Works perfectly for me. no wavy borders either.

I have made a lot of piano key borders and love to do them. If I come up short or just a little too long for the sides of the quilt, I just take a small seam in a few keys and it all seems to work out and it is definitely not noticeable. I usually make the corners with a solid piece of fabric or make a pinwheel block and that can be sized very easily. Good luck and I am sure you will be able to fit your border easy.

Ladies....YOU ROCK! I got the border keys on the quilt top today! I did exactly what you suggested and it worked. I had to take seams in just a little.

So, I have a 1 1/2"black border, 3 1/2"piano key border. Now I want to add another black border. How wide do you think it should be?

I run the keys up the sides and use a square in the corners

So gald you got it to work!!! I'd go with about 4.5- 5 inches for the outer border. Can't wait to see your quilt!

When I use piano keys on a border, I usually foundation piece onto a piece of muslin that I have cut to size. That way I don't have to worry about the border stretching or being the wrong length; however, I usually do random width keys rather than identical width keys.

I sew (stay-stitch) a piano key border (or any border with lots of pieces) about 1/8 inch from the edge to keep it from coming apart.

Me, too. A vital step, inho.