Oops, you were talking how to attach borders. I used to do the measure the middle of the quilt and cut my border measurement to that. Then I realized why measure? So I lay my quilt out and lay my border fabric, already cut to the width I want and pieced if needed, over it in the middle (not along the edge). Line up one edge of the border with edge of my quilt then smooth it out and mark the border fabric for cutting even with the opposite edge of the quilt top. I then cut two borders to that size (Usually I do sides first). Attach them to the quilt and do the same for top and bottom.
If I have cornerstones, I measure. If it is pieced I also measure and figure out the piecing that needs to be done to come up to that measurement.