The other day, someone here in the office rented a copy of the 1976 movie Bound for Glory.  It's the story of Woody Guthrie, the singer of mournful songs from the Dust Bowl days of the 1930s, when a severe drought turned thousands of Great Plains farm families into refugees.

Our colleague liked the movie, particularly its use of authentic, but beat-up, old automobiles that we call "jalopies."

This got us wondering: Do the movie studios have a vast warehouse full of junkers as well as clean and polished classic cars? You see them, too, in period movies. Is this some sort of editing trick?

Turns out, until the 1970s, many studios did store hundreds of vintage cars on their backlots. But when Southern California land became too valuable to hold onto, they sold off the fleet and began renting old automobiles for their films. Wealthy California car collectors dominated this business.

But then enterprises like the Web site began searching out cars, trucks, motorcycles -- even old buses -- all across the nation.

That's because movies, commercials, music videos and coffee-table photo books are being shot in all kinds of places. Filmmakers even pay to ship some vehicles thousands of kilometers to the set. Owners of old cars can make $300 or $400 a day, often much more. Sometimes they go along and meet movie stars and directors.

As for those visual tricks, in this computer age techno-wizards can take 20 or so cars and multiply them into what looks like a huge parking lot. But the filmmakers still need those 20 cars. And lots of someones, somewhere, are making a nice chunk of change renting them to Hollywood.