Tent Sidewalls - Cathedral Windows and non-window

Each side panel is 7' x 20'.

For a 20' x 20' Tent:
To leave one 20' side of the tent open, you need to rent 3 panels.

For a 20' x 40' Tent:
To leave one 40' side of the tent open, you need to rent 4 panels. 
To leave one 20' side of the tent open, you need to rent 5 panels.