Guy goes to a cocktail party but doesn't realize his fly is open.
At the party he spots a real pretty gal across the room and decides to try his luck. He walks up and they start chatting when the gal glances down and sees his open fly. Hoping to be discreet she casually asks: "Did you lock up your business before you got here tonight?" The guy says, "Sure."
After a few more minutes of small talk the gal tries again: "Are you sure the store is locked up?" The guy says, "Absolutely..." still not realizing what she meant.
As he walks away a few minutes later he realizes his fly is open and fixes the problem. Later that evening he spots the gal again, only this time he is prepared. He walks up behind her and taps her on the shoulder. As she turns around he smiles at her and asks: "Remember earlier when you noticed my store was open? Tell me... was my best salesman in or out?"