Measuring and Cutting a Mat Board

[@scoobylyn]

Fantastic video. I've been looking for a T square like yours but can't find one. Where did you get yours and what length is it?

[@gigiartstudiowithartistvir3919]

I'm trying to find a video on how to cut the outside edge of the matboard so it's straight on all sides. How did you cut it without it slipping all around and going crooked?