I want to block out polygon areas, then move the vertices around while stretching/shrinking the attached lines. Hmmm... poor explanation there.
Say I have 2 adjacent squares, so they have one side and two vertices in common, as well as each having 2 vertices and three sides solely of their own. Imagine a domino laying horizontally.
I want to be able to grab that middle-upper vertex and pull it up, stretching all the lines so that the 2 squares are now 2 halves of a house.
I think a drawing will best demonstrate what I want to do:

I would like to start with the drawing at the top, grab the red dot and drag it to produce the configuration at the bottom.
Thank you for any help!