Ports are used to link documents from inside of a folder to outside of the folder. They are automatically created when you create a covering link between a folder and a document. In the most basic case, create a document and a folder in the project. Draw a link from the document to the folder. Navigate inside the folder, and notice that you now have a port into the folder. If you reverse the arrow in the top-level of the project, you will notice that a port will open toward the covering document.
Allen P
NI