Page 2

Move the duplicate so it right next to original.

(Click for larger image.)

Image > Zoom in by 1.
(You may want to do this again.)

Click on your deformation tool.

Grab the middle right node and move it in about 3/4 of the width of the upright.

Hold down the Ctrl key, now grab the top right node and move it downward.

Now you may want to move that center right node in a little more to make it a bit skinnier.  Once you have it the way you want go to the Tool Options box and click apply.  Use your mover tool and line up the side board with the main upright. 

Colors > Adjust > Brightness/Contrast > these settings:
Brightness -30
Contrast -15

Layers > Merge > Merge Visible.

Rename this layer upright.

(Click for larger image.)

Page 3