Perfect Squares works with the same “catch lip” system we use with the “Perfect Layers” border tools.
The lip of the square catches the edge of paper or photo you want to crop, giving you perfect right angles and squares.
When I have a photo I want to quickly crop, I find it painful to pull out the trimmer.
I used to just grab a ruler and a knife, and “eyeball” it, but I found I always end up a little bit off. Not anymore! This is where my Perfect Squares really comes in handy for a quick photo crop.
I just hook the lip (green line in picture below) on the edge of my photo, and slide it along until the right side (red line in picture below) is lined up where I want to cut, and I have a perfect 90-degree angle to cut!