Boolean Difference when the shapes aren't intersecting?

Rhino Rhino for Mac
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1

Hi all,

I am trying to boolean difference two shapes, but I usually use this command when a shape is intersecting. Please see my image below for reference - is there a way that I can boolean if the cutting shape is fully inside the first?

Excuse my terrible wording!

Thanks!

Screenshot 2020-04-15 at 19.19.38|690x432

2

Hello - no, there must be some connecting surface - if the goal is to make a mold, split the box first along the parting line into the two parts that would make the mold.

-Pascal