Is there some type of mask to hide parts of the model so it looks cleaner to do callouts?

I have a part of the model that I am zooming in on and want to callout out different parts. Is there a way to mask part of the model to center it in the size of the page and do callouts around the model? I tried to use a border, but it only goes to 10 pt. That is not enough to make a difference. Any suggestions?