Juan comes up to the Mexican border on his bicycle. He's got two large bags
over his shoulders. The guard stops him and says,"What's in the bags?"

"Sand," answers Juan.

The guard says, "We'll just see about that ~ get off the bike."

The guard takes the bags and rips them apart; he empties them out and finds
nothing in them but sand. He detains Juan and has the sand analyzed, only to
discover that there is nothing but pure sand in the bags.

The guard releases Juan, puts the sand into new bags, hefts them onto the
man's shoulders, and lets him cross the border.

A week later, the same thing happens. The guard asks, "What have you got?"

"Sand," says Juan.

The guard does his thorough examination and discovers that the bags contain
nothing but sand. He gives the sand back to Juan, who crosses the border on
his bicycle.

This sequence of events repeated every week for three years.

Finally, Juan doesn't show up one day and the guard meets him in a cantina
in Mexico.

"Hey, Buddy," says the guard, "I know you are smuggling something. It's
driving me crazy. It's all I think about. I can't sleep. Just between you
and me, what are you smuggling?"

Wanna guess what he was smuggling???

Juan sips his beer and says, "Bicycles."