Hey Wheels, you think like a male engineer
. Sometimes you have to think like a woman using the female side of your psyche (assuming that such a thing exists in us males although I am assured by the "other" gender that, most assuredly it does and that, if you exercise it, you just might get your "way" more often....it's kinda like eating pretzels without drinking beer).
I think, therefore, that it was meant to be:..."provide shade (during the day) and ventilation at night".
BTW, I also have trouble with these things but I'm trying to figure these things out in my advancing age so that I woun't be sailing solo.