The opening is the visible portion of your artwork. On pictureframes.com, all you need to do is enter the size
of your picture. We will automatically make the mat opening ¼" smaller than your art size on each dimension.
This will keep your art from falling out through the mat opening. For example, when ordering, if you select a
picture size of 8" x 10", the mat opening will be automatically adjusted to 7¾" x 9¾".