The clerk replies, "You mean two-by-fours, don't you"?
The guy scratches his head and says, "I'll go check", and goes back to the truck.
He returns and says, "Yeah, I meant two-by-four".
"All right. How long do you need them"?
The guy pauses for a minute and says, "I better go check." After a while, he returns to the office and says, "A long time. We're gonna build a house".