Two Irishmen Were Hammering Floorboards Down In A House....

Joke: Two Irishmen were hammering floorboards down in a house. Paddy picks up a nail, realizes it's upside down and throws it away. He carries on doing this until Murphy says, Why are you throwing them away?" "Because, they're upside down", says Paddy. "You daft twat!", replies Murphy, "Save'em for the ceiling!"