Boolean

 From:  Derek (SANGKYU5)
3280.1 
Hi,

I attached a sample file to ask you how to make a mold.
When you open it up, you will see a box and a feature on the left side.
I tried to put the feature in the box and then used "Boolean - Diff" to make a mold. It didn't work.
Do you have any idea how to make it work?
Attachments: