Matting photos make them complete and professional.
First, choose the mat color you would like. I usually stick to black or white.
Measure the length of the photo. Subtract the length of the photo from the length of the mat. i.e. if you have a 10 inch photo and a 14 inch mat, you'll have 4 inches.
Divide that number in half. That number is the amount of mat you should have on each side. So, using the previous numbers, 4 divided by 2 is 2. So, you will have 2 inches of mat on each side.
Repeat this for the height of the photo.
When you found your vertical and horizontal numbers, measure from the end in with your vertical number and make a mark towards the bottom of the mat. Measure in from the top of the mat and make another mark. Draw a line between the marks. That will be your 2 inch border.
Repeat this for the other vertical and both horizontal lines.
Now that you have your square drawn, get out your bevel mat cutter.
Line up a line from your drawn square with the cutter so that the square is on the inside. i.e. if the blade is on the left, the square should be on the right.
Make your first cut, rotate 90 degrees and make the next cut and so on.
The middle should fall out after the last cut.
There you have yourself a window mat.