Standard Workflow for Using Perforators

Create a parametric cell having a parametric solid(s).
Use the Perforators tab in the Parametric Components dialog to tag the parametric solid as a perforator.

Note: The Hide After Placement in the Perforator tab controls the visibility of the perforator parametric solid while placing as a cell.
Attach the parametric cell to the DGN file that contains the target element on which the perforation is to be performed. The target element can be a parametric solid or a SmartSolid.
Hover the cursor on the target element, such that the parametric cell overlaps the target element. Observe that the perforator previews as a blue dotted line.
Place the cell on the target element. Observe that the perforator cuts the target element to the shape of the perforator.

Additionally, you can also apply variations to the perforator. So, in case of the door-wall example, you can apply variations for different door sizes and the cut in the wall will change according to the door size.

Once placed, the parametric cell containing perforator acts any other parametric solid. You can manipulate the cut using Move and Rotate commands. Also, deleting the placed cell undoes the cut on the target element.