- 1). Choose two different colors of mat board that will compliment the picture. Place the darker color, which will be the bottom mat, face down on a flat work surface. Use a ruler to measure 2 1/4 inches inward from each edge of the mat. Use a pencil to draw a line down each side of the mat to mark the measurement.
- 2). Cut the bottom mat using a razor knife. Position the ruler along one pencil line and insert the knife into the mat where two of the pencil lines intersect. Pull the knife down the line slowly and carefully, using the side of the ruler to steady the cut and ensure the line is straight. Stop cutting when you reach the next point where the lines intersect. Repeat this process along the three remaining sides of the mat. Pop out the cut piece of mat to create the window.
- 3). Place the lighter colored mat, or top mat, face down on the work surface. Use the ruler and pencil to measure 2 inches inward from each edge and and mark lines in the same manner as before. Cut along the lines with the razor knife, using the ruler as a guide. Do not cut past the point where the lines intersect. Pop out the cut piece of mat and discard.
- 4). Apply rubber cement or double sided tape to the back of the top mat. Place the bottom mat face down on top of the top mat. Line up all edges before pressing the mats together. Rub your hands over the surface of the mat while pushing down gently to secure the mats together. Turn the mat over to check your work. There should be an even 1/4 inch border of the bottom mat visible through the window.