A young guy joins an order of monks and eventually when he's fully accepted, he's sent to a mission in the middle of the African Jungle. He gets along fine with everyone, they all get along fine with him, but something is bothering him, "what can it be?" he asks himself. So off he goes to see the Abbot to ask if he can fathom out what's bothering him. "It's your desire to have sex" says the Abbot "We in this order are very tolerant of a young mans' needs, and to that purpose we have provided a simple cure. Do you see that barrel in the corner over there? The one with the hole in it?" "Yes" says the young monk "Well" says the Abbot "You can use that barrel hole to relieve yourself, any night of the week, except thursday" "Why not thursday?" says the young monk.

The Abbot replies "Thursday's your day to be IN the barrel"