The Creative Grids rotating cutting mat makes squaring up blocks up to 14" easy and efficient.  Rotating mat is self-healing, and rotates a full 360 degrees.  It's marked with a 1" grid that includes 1/8" markings, as well as 45 and 60 degree angled lines.  No matter what side of the mat you're working from, you'll always have a set of numbers to read that are right side up.  The non-slip base gives you a stable cutting surface and is light-weight for taking along to retreats.