A college teacher noticed that his exchange student, Dave, suddenly had started attracting a lot of female attention.

So, one day he asked Dave about his secret. Dave replied: "Well, before sex I simply whip out my willy and smack it against the bedside table, like a hammer. It numbs it up and makes me last longer".
Later that day, the college teacher gets home to his wife and finds her in the shower - a welcome opportunity for sex. So, he quickly undresses and starts banging his dick against the dresser, just before hearing his wife calling from the shower:
"Is that you, Dave?".