I'm a complete sketchup noob. I've been learning to navigate sketchup for some wood working projects. I have a model that i downloaded from the warehouse and i managed to resize it to my liking. The model has rounded corners and it makes it a little difficult to get accurate measurements for a side panel.

I was wondering how i can remove the corners from a model so that two straight lines intersect at 90 degrees? Any help the community can give me would be great.