CONVTOSOLID command
Converts entities to solid entities.
            Description
Converts valid 2D and 3D entities to 3D Solid entities. Valid entities include:
      - Watertight 3D Mesh
 - Watertight 3D Surface
 - 3D Polygon Mesh
 - 3D Polyface Mesh
 - Circle with thickness
 - Closed Polyline of non-zero thickness and uniform width
 
Method to convert to solid
There is one method to convert entities to 3D Solid entities:
         - Select entities
 
- Select Entities
 - Begin converting an entity to a 3D Solid entity by selecting a valid entity then:
 - Select entities
 - Select another valid entity or press Enter to complete the command.