Earth Tube Modelling

[jacksym]

Hi,
I am trying to follow the IES Earth Tube Modelling pdf guide but just wish to clarify a few things.
I have managed to draw a tube a minus level but after some help with the following:
1. What has been used to create the openings on the top (ceiling) surface at each end?
2. Is the top (ceiling) surface at ground level (0m) or does it need to penetrate beyond into the zone?
3. Has a normal opening been inserted at each end of the horizontal tube?

Thanks

Jack