Geodesica version: 0-9-6-0. The Extrude tool looks like this and is located on the Modify Tab of the Toolbar. This tool extrudes a face. Click the Extrude button. The value field appears on the modify tab; enter the extrusion distance. Geodesica prompts you to pick a primal face.
If the Control key is DOWN the envelope Normal at each vertex is used as the extrusion vector. If the Control key is UP, the face normal is used as the extrusion vector for all vertices in the face (default behaviour).
If the Shift key is DOWN the operation is applied to all facets in the clicked manifold.
Above: the Kill Vertex tool was used on a seed corner to create a pentagonal face; then the Extrude tool was used repeatedly to create a stand on the bottom of the dome.
Note: there are no hidden interior facets or “walls” between the extruded face and the original face; the space inside an extruded face is continuous with the rest of the dome.
To control hubs around extrusions please see the page Hub Context Menu