Need help adding borders

[MayinJerset]

I've been helping my sister with a queen size carpenter's wheel quilt kit, she has finished the big center Carpenter's Wheel pattern and is now ready to begin adding the first of several borders. I usually slap and sew my borders but this is a big quilt and I don't want her to end up with wavy borders or what her long arm quilter calls "lettuce".

First border in a thin one on the top and bottom to make the quilt rectangular. I know she needs to measure the width of the quilt on the top, middle and bottom. If they are all the same that is the length she cuts her border. My problem is what to do if the measurements aren't the same in all 3 places. I'm thinking she needs to use the center measurement but aren't too sure. Need to advice of all your seasoned quilters. May in Jersey

[bonniebella]

I would not consider myself a seasoned quilter but, I was taught to measure top, middle, bottom and average it. What I usually do is measure through the centre and use that measurement.