Measure the outer edges of your art work and decide how many inches your mat will be. Generally, you want an exterior mat to be between three to six inches wide, with the bottom border 1/4- to 1/2-inch wider to give the art piece height. If you want a six-inch mat around your 8 x 10 art piece, you'll want the outer dimensions to be 14 x 16 1/4 (allowing for the extra 1/4 inch at the bottom border). Make your line measurements on the back of your mat board using a ruler and pencil.
Place a metal ruler against the marked line on the back of the mat board. Place the box cutter blade exactly on the pencilled line. Press the knife slightly into the board and run it against the ruler to make your guide cut. Pick up the knife and take it to the starting point on your ruler guide. Press the cutter down again and continue cutting until you get to the end of your guide cut. Repeat the process several times until the mat is completely cut through. Repeat the process on all sides. Be sure to use another cutting mat or something on the table so the mat cutter does not damage the table.
Measure the inside edge of your mat, allowing for the 1/4-inch margin all around. So, if your painting is 8 x 10, then your matting measurement should be 7 3/4 x 9 3/4. Mark your measurements with pencil.
Place the Logan mat cutter on top of the back of the mat and align it with your interior cut pencil line. Place the mat cutter blade on the pencil line at a corner and tighten the Logan holding screw. Press the razor blade down to begin the cut and slide it down the ruler as you are pressing the guide cut. Lift the blade up and return it to your starting point. Repeat the process several times until the mat is cut through. Lift the mat cutter blade up and place on next cutting line. Start cutting in the corner again and repeat the cutting process several times until the mat is cut. Repeat for each side.
Gently remove the rectangle from the center of the mat and place your art work there. Hold the art work in place with a piece of masking tape adhered to the top of the back of the art piece and the mat board, and do the same for the bottom of the art work.