Closed Polygon to Polygon Section command, the closed area created by the line is converted to a polygon section. With this method, sections are defined in the desired forms.
Location of Closed Polygon to Polygon Section Command
You can access it from the ribbon menu Modify tab under the Transform heading.
Create a closed area with the line.
Click the closed polygon to polygon section command.
The Section Settings dialog will open. Set your section name and material.
Click the OK button to close the dialog.
The section you define will be listed under the Sections row in the Structure Tree view .
Structure tree before polygon section is formed
Creating a closed area with a line
Selecting the area to be transformed to a polygon section
Editing the settings
Creating a polygon section and adding it to the structure tree