How to crop just one shape

Hi all,
I have a model that consists of two separate sets of polygons. Each appears solid but there is no stencil being used. I need to crop each however. Is there a computationally inexpensive way to do this?
I’m trying to avoid modifying any polygon coordinates but I could do that if necessary.

What do you mean “crop”? I don’t understand the meaning of crop in relation to sets. Cropping to me means limiting a region on the screen like cropping an image. What are you cropping and what do the sets have to do with it? Do you want to crop everything that doesn’t fit inside either set?