Topic Title

Can an edge of a void align with an edge of a master slab/polygon. Or do I need to add vertices's to an edge of a slab/polygon

The latter is the way to go.

[Mark F. Madura]

I recommend using Covered Polylines, and voids can be coincident, overlapping, or completely outside of the master boundary. You can also put a 'notch' in one edge of the master boundary instead of making the void coincident with it.