Southern Hospitality

Nate and Martin, two army buddies are on leave and decide to go to Nate's house and get drunk. Lo and behold they run out of beer so Nate says that he will go for more. As he is leaving he tells his wife Barbara to show Martin her best southern hospitality which she agrees to do. Nate comes back with the beer and finds Martin and Barbara screwing right on the kitchen floor.
Nate yells, "What are you doing Barbara?"
She replies, "You told me to show Martin my best southern hospitality."
Nate replies "For cripe sake woman, arch your back, poor Martin's balls are on the cold floor."