Originally Posted by RedGarnet222
The trick is to press the seams to be sewn in opposite directions so you have opposing seams to match up as they are sewn. That gives you a great little ledge that locks them into place.
That's exactly right but sometimes that just isn't enough. That's why I put a pin in each of those seam allowances plus one just a hair to the left of the left one. Learned that on this board. Have made 3 or 4 quilts using that technic and it's worked every time.