When trying to draw a Slab Hole, an Information message tells me,
"A slab hole must be placed inside a slab."
What exactly does this mean?
By definition, a hole in an object such as a slab must be completely contained within that object. The hole cannot touch the edge of the object, extend past the edge of the object, or be contained by multiple objects.
To draw a slab hole
Select Build> Slab> Slab or Slab with Footing from the menu, then click and drag to draw a rectangular slab.
Click on the slab to select it and edit its size and shape as needed.
Select Build> Slab> Slab Hole from the menu, then click and drag to draw a small rectangular slab hole entirely within the existing slab.
Slab Holes can be drawn within either a Slab or a Slab with Footing.
Slab Holes with Footings can only be drawn within a Slab with Footing
Once drawn slab holes can be edited much like slabs can. The only restriction is that they must be contained entirely within one individual slab object.
You can see the results in a Camera view.
If you need to create a cutout in the slab's perimeter rather than add a hole to its interior, you can add breaks to its edges.
To add edges to a slab's shape
Click on the slab to select it, then click the Break Line edit button.
Click on an edge of the slab where you would like to add a corner.
When you click, a new diamond-shaped Reshape edit handle is created.
Don't worry about placing the new corner with precision - the shape can be edited accurately later.
Click and drag the square Move Line Segment edit handle to move the edge on either side of the new corner.
The new edge can also be moved using dimensions.
You can also click and drag the Reshape edit handle at the new corner to change its location and the angles of the adjacent edges.