I've been doing a lot of perspective work lately, and even with my ruler, I find that I have a really hard time eyeballing weather or not a line is square on my notebook page. Since a standard T-square is a little too big and bulky to use on this size paper, I've been struggling with squareness.
This wouldn't usually be a problem, but I'm working with perspective, and having straight, square lines is important!
So, to you guys that are more experienced then I am...I have a question: What tricks do you guys use to determine if a line is square or not??