Snap Points and Force No Ground and Structure Linking


does anyone know what these are supposed to do or mean?

When I have “Snap Force No Ground Requirement” unticked my structure does not snap to other structures, when ticked it will. Is there a setting that sy a structure must be on the ground that I have missed?

Also the Invalid Structure Linking, what does that mean? Is it related to when you demolish one thing and half the base collapses?