3 men were driving through the desert when their car broke down. So they had to get out.
The first man took out a bottle of wine with him, the second man took an umbrella and the third man took the car door.
On the way, they meet another man. He said to the first man, "I know why you have got the wine, so you can have a drink when you are thirsty."
He said to the second man, "I know why you have got the umbrella, to keep the sun off you."
"But," he said to the third man, "Why have you got the car door?"
And the third man replied, "If I get hot, I can wind the window down!"