Lengthens or shortens structural members to meet a plane.
Access Methods
Ribbon: Structure tab 
Modify panel Extend Member 
Command entry:
plantsteelextend
List of Prompts
The following option is displayed.
- Select structural member to extend or shift-select to trim or [Undo]:
-
Click the structural member to extend. Shift-select trims the selected objects rather than extending them.
Note: To switch to plantsteeltrim, hold down SHIFT and click the member you want to trim.