Trelis 16.4 User Documentation
The separate surface command is used to separate a surface from a sheet body or a solid body.
To separate a surface from a body
Separate Surface <range>
Separating a surface from a solid body will create a "hole" in the solid body. Thus the solid body will become a sheet body. The newly separated surface will be also sheet body, but it will have a different id. Multiple surfaces can be separated from a body at the same time, but each separated surface will result in a distinct sheet body, as if the command had been performed on each surface individually.