You can also access this functionality from the ribbon by clicking 
  Find
. 
 <code name>. The boundary is added to the corridor surface.
You can also access this functionality from the ribbon by clicking 
  Find. 
You can also access this functionality from the ribbon by clicking 
  Find
. 
The boundary is added to the corridor surface.

A closed polyline is created as the outer boundary of the corridor. This closed polyline can then be used to create a surface boundary, using the Add From Polygon command.