To delete balusters and posts from a railing, you must modify the railing type. 
-  In a plan view, select a railing. 
-  On the Properties palette, click  Edit Type. Edit Type.Note: Changes made to the type properties affect all railings of this type in the project. You can click Duplicate to create a new railing type.  
- In the Type Properties dialog, for Baluster Placement, click Edit. 
- In the Edit Baluster Placement dialog, under Main pattern, select the baluster or post to delete. 
- Click Delete. To leave a space in the pattern where a baluster or post currently exists, for Baluster Family, change the value to None.  
- Click Apply to preview your changes in the model. 
- Click OK.