Extra Stupid Window Stickers

[Mallardsx2]

Not a sticker, but can anyone tell me what the rear window ventilation is for? It was going into a Rubbermaid tote in the back it looked like.
View attachment 397783

It’s a ram and the heater core costs $2500 to remove and replace.

 

[Bowmannate2000]

Diesel heater. #vanlife

That's the conclusion I came to after thinking about it some more.