Is there a simple or easy way to put "cornerstone" in the border fabric--like at the corners and in the inner borders? I have a hard time making it straight.

How do you add them?

I just measured the block and added them in the border. But it seems to me there must be an easier way to get them straight in the border. Others on this board seem to have them so exact. My quilt has four blocks connect with a "cornerstone" in an inner border. Does that make sense?

This is how I do it. Let's pretend that your blocks are 8.5" square before finishing and you want 2" sashing. First cut a 2.5" strip. I find that if I cut the sashing into 8.5 X 2.5 inch rectangles first, I'm more accurate. Sew the sashing to your blocks to form a row. Press all seams toward the sashing. Now you have a row done. Next, cut a piece of the sashing fabric 10 X 8.5, and cut a piece of cornerstone fabric, 2.5 by 10". Sew the 10" sides together. Press away from the cornerstone. Now slice this piece into 2.5 inch strips. You will have 4 strips mostly sashing with a little cornerstone fabric at the end. Sew these together to make as long a strip as you need to match your block strip. You may need to add or remove a cornerstone at the beginning or end of this strip. Press all seams away from the cornerstones. Sew this to your block strip, matching seams.
A couple of things: if you cut your sashing to size before adding it to the blocks you will be more consistant. If you press the seams in the way I indicated, the seams will 'lock' together making the piecing easier. And lastly, I just used 10 inches for the example above. You can cut the rectangle the size of your block X a number that's a multiple of your sashing width. The sashing in the example was 2", so add seam allowances you get 2.5". 2.5 X 4 = 10", but you could also make it 20" or any length and just cut 2.5 inch strips.
Hope I didn't confuse you more. ;-)

PaperPrincess, that is pretty much how I do mine too. First sew the sashing on two opposite sides, then sew the corner stones to the sashing for the other two sides. As long as the measurements are correct and the seam allowances are even, the pieces should match.

Thanks, Ladies, for your help. I am working on it. I have one set of sashes and cornerstones sewed between two rows of blocks. i appreciate your help.