A cyclist with panniers was stopped by customs at the border. "What's in the bags?", asked the officer, pointing to his panniers. "Sand," said the cyclist. "let me take a look", said the customs official. The Cyclist did as he was told, emptied the bags, and proving they contained nothing but sand, refilled the bags, and continued across the border.
A week later, the same thing happened, and continued every week for a year, until one day the cyclist with the sand bags failed to appear.
A few months later, the officer saw the cyclist living it up in a nearby town. "You really fooled us", said the cop. "We knew you were smuggling something across the border. I won't say a word - but what was it you were smuggling?

"Bicycles!"