A man riding a bike and carrying two sacks on his shoulders was stopped by a guard while crossing the border.
“What do you have in those bags?” asked the guard.
“Sand,” the cyclist replied.
“You’ll need to open them so I can take a look inside.”
The guard emptied the bags and found out they did indeed contain nothing but sand. The man put his bags back on his shoulders and continued across the border.
This happened a couple of times each week for a month. Sometime later, that same guard ran into the cyclist in the city.
“Hey, where have you been?” the guard asked. “You sure had me wondering. I know you were smuggling something across the border. If you tell me what it was, I won’t prosecute you. What was it?”
The man smiled and said, “Bicycles!”