When customizing curtain panels in a curtain wall, you can exclude segments from the grid to achieve the desired result. 
 Video: Place Curtain Grids 
- Click Architecture tab
Build panel
 (Curtain Grid). 
 
-  Click Modify | Place Curtain Grid tab
Placement panel
All Except Picked. 
 
- Place the cursor on a curtain wall, so that a preview of the curtain appears. 
 
- Click to place the curtain grid. 
  
The curtain grid line is displayed in red. 
  
 
  
 
 
- Click segments of the curtain grid to exclude them from panels. 
  
When you click the segments, they are displayed as dashed lines. 
  
 
  
 
 
- When you finish excluding segments, click Finish Current to place a new curtain grid.