Measure the photo or artwork. Determine how much of the image that you want to remain visible. Use a ruler and pencil to record the measurements. The inner dimensions of the mat board need to match the measurements. For example, if your measurements are 4 inches by 6 inches, an 8-inch by 10-inch piece of mat board gives you a 1 1/2-inch to 2-inch border on all sides of the mat board, which is standard for many professionally framed artworks.
Prepare your style of mat board cutter. There are different brands and styles of mat board cutters, so follow the instruction manual that came with your cutter.
Position the guide rail and cutter according to the dimensions of the mat board.
Cut out the mat board. Leave a 2-inch border around the inner dimensions of your mat board. Cut the board 2 inches away from the edge of where you will cut out the inner piece of mat. Once again, if your inner cutout measures 4 inches by 6 inches, with a 2-inch border, the total mat size is 8 inches by 10 inches.
Cut out the inner section of the mat board based on your measurements from Step 1. Try to cut the 90-degree angles as perfect as possible as you move the cutter in the corners of the mat board.