1. Place your mat, which should be already marked for cutting, face down on a surface suitable for cutting.
2. Place your metal edge on the outside edge of one of your boarder lines. Place your cutter flush with the metal edge. Your mat cutter will always be placed on the interior of the window being cut. The metal edge will be on the exterior.
3. Position your cutter so that the white hair line on the right of the cutter is exactly aligned with the top boarder line. This line will be perpendicular to the one you are about to cut. See diagram B.
4. Place your index and middle fingers over the chrome handle and push the blade into the mat. Push all the way down. See above for adjusting blade depth.
5. Holding the blade down, pull the cutter toward you along the metal edge. Stop when you reach the bottom line. The white marker line will be exactly aligned with the bottom boarder line when you are done.
6. Raise the blade by releasing your fingers. You may have to gently pull it up.
7. Rotate the mat clockwise until all for edges of the window have been cut.

If you are very lucky your mat window will just fall out. Most likely this wont happen at first, but by experimenting where you start and stop your cutter you can make this happen. Of course, your are always trying to avoid an over cut which will ruin your mat. An over cut is one which extends beyond the stopping point continues to far into the mat.

If your mat window does not just fall out, you will have to help it by hand cutting the corners just a bit. This can be done effectively with a sharp utility knife. With the good side of the mat up, place the knife in from the top, keeping it aligned with the 45 degree bevel cut. Pull it toward you until the corner is cut free. This will take a little experimentation, but is very easy once you get the hang of it.

Change Blades Often

The key to clean mat edges is new blades. Change them after every two or three mats. You will learn this the hard way. Blades cost pennies; mats cost dollars.