While crossing the US-Mexican border on his bicycle, a Mexican Jew by the name of Jose Cohen was stopped by a guard who pointed to two sacks that Cohen had on his shoulders.
"What's in the bags?" asked the guard.
"Sand," said Cohen.
"Get them off - we'll take a look," said the guard.
Cohen did as he was told, emptied the bags, and proving they contained nothing but sand, reloaded the bags, put them on his shoulders and continued across the border. Two weeks later, the same thing happened. Again the guard demanded to see the two bags, which again contained nothing but sand. This went on every week for six months, until one day Cohen failed to appear.
A few days later, the guard happened to meet the Cohen downtown.
"Say friend, you sure had us going crazy," said the guard. "We knew you were smuggling something across the border. I won't say a word - but what is it you were smuggling?"
Cohen responded with a grin, "Bicycles!"