One day a boy walked into a pharmacy. He walked around for a while until he found what he was looking for. He grabbed a box of ribbed condoms, walked up to the checkout lane, and slapped them on the counter. The sales clerk, looking suspiciously at the young boy, said, "Well son, here you go, that'll be £2. The boy pulled out a £5 note, handed it to the man, and the salesclerk asked him, "Now, boy, do you know what the ribs are for?" 

The boy answered, "No sir I don't, but they sure make the hair on my goats back stand up!"