The police had the all the prostitutes line up in a straight line on the sidewalk, just as grandpa was passing by. As soon as he noticed his  grandson, he stopped and asked him what he was lining up for.

Not wanting his grandfather to know the truth, the grandson told grandpa that someone was passing out free oranges and he was lining up for some.

"That sounds good. I think I'll have some too," Grandpa said, as he made his way to the back of the line.

A policeman went down the line, questioning all the prostitutes, until he reached grandpa. Looking very bewildered, he said to him, "You're so old, how do you do it?"

"It's easy," replied Grandpa. "I just remove my dentures and suck them dry!"