Two guys met in the middle of the desert. One was carrying a car door, the other an umbrella.
The one with the car door said to the guy with the umbrella, "Why are you carrying that umbrella around, it isn't going to rain in the desert?"
To which the guy with the umbrella replies, "Yeah", but it keeps me out of the sun! By the way, why are you carrying around that car door, you don't even have a car to go with it"
The guy with the car door says, "Yeah, well at least if I get too hot from the sun I can just roll down the window!"