INTERSECTEDENTITIES system variable
Determines how to modify entities that intersect with the extruded/revolved entity when the Auto option of the EXTRUDE or REVOLVE command is selected.
The INTERSECTEDENTITIES system variable is one of the four system variables found under the Extrude mode group.
0 to 2
0 - for Workspaces Drafting and Modeling
1 - for Workspaces Mechanical and BIM
0: Do not modify the parent entity.
1: Subtract the created entity from the parent entity.
2: Unite the created entity with the parent entity.