Without scripts: Extrude the border, select the newly extruded faces (ctrl-clicking the face level to convert selection from edge to face), switch back to edges and delete the selected loop for cleanup. Free script alternatives: Extend Surface (UI-less) Extend Borders (with UI)
The best example I can think of is this: Question: How can I quickly add loops? Right now I am clicking Cut and than add the edges click for click. Answer A: Oh that is really time consuming, clicking that button, you can just use alt+c for the Cut-Tool. Answer B: Wow that is crazy, you can just select a edge in a ring use…