Block Types
        Three types of block are available:
         
        
            - Building Blocks 
 are used to draw the model or a section of the model.
 
            - Outline Blocks 
 are used to help in the creation of building block geometry and do not 
 affect the model.
 
            - Component Blocks 
 are used to create visual and shading structures which do not contain 
 zones.