1.  Fold the pieced backing in half by placing the two  long side edges together.  Hold the backing by these edges and check to
see that the fold that you just made is hanging straight.

2.  If the fold does not hang straight, slide the edges in opposite directions until it does hang straight.  This will probably mean
that the edges do not meet exactly in a straight line.

3.  Take the fold hanging at the bottom and bring it up to the first edges.  You will now have four layers of backing fabric.  Check to
be sure that the new fold hangs straight and adjust if needed.

4.  Continue bringing the last fold up to the first edges and adjusting as needed until the width is small enough to fit across your
largest cutting mat.

5.  Place the backing fabric on a table or the floor.  Place a cutting mat under one edge of the folded fabric.  Starting from the
outside edges and going in, find the place where all of the layers of the backing are present.  Place your ruler along this location.  
Trim off the excess, uneven layers.

6.  Trim the other side in the same manner.

7.  To square up the side edges, begin by bringing together the top and bottom edges that you just trimmed.  These edges
should be straight with each other.  Repeat steps 2-6 above.

8.  * Note- backing size

For use with tops to be Longarm quilted:
Measure the squared backing fabric to make sure that it is still at least 8 inches larger than your quilt top in
both directions.