A border policeman was on duty when he saw a man riding across the barrier in a bicycle with two large sacks.on his shoulders. He stopped the man and asked what he was carrying, the man looked at the policeman and said, “sand.” The police didn't believe the man and motioned him aside, where he asked to search the bags. He found nothing but actual sand. Even the lab confirmed it was ordinary sand, hiding nothing. So he let the man go. Next week he saw the same man with similar sacks again. And again, he asked, again got “sand” and again confirmed, nothing but sand. After the third time he decided to just let the man pass.
Years later, after retiring, the policeman happened to run into the same man at a border bar. After greeting him the policeman said, “You know, I always suspected you were smuggling something, but I could never prove it. Now that I'm retired and no longer have any power to arrest you, could you tell me what it was?” The man looked at the policeman slyly and said, “Bicycles.”