How to slide a Vertex or Edge outside of the border

Problem:

When you press G twice, you know that you can slide the vertex or edge loop but you see that it doesn't let you move further the current boundary/limit of the vertex or the edge.

How to slide outside of those boundaries?

To be able to slide towards exterior, further the boundries of the form, after pressing G twice, press on ALT while moving and it will slide the vertex or the edge loop that you selected, outside the boundries.