Today my daughter and I created this great album designed by Kathryn at Kathrynscraps. You can purchase the pattern here.
In the instructions, you are told to trim your pocket corners off at an angle. You can use your Perfect Trim ruler to make the trim.
The first thing you do is to score the sides and bottom at 1/2" per the instructions, then add your tape. Place the pocket on your cutting board, tape side down.
Place the point of your craft knife in the center of the intersection of the score lines.
Place any one of the lines from the center box on your ruler on the edge of the pocket and scoot the ruler up to the knife as shown below. Trim off the edge at a perfect 45 degree angle!