Each day, up to 250,000 Americans make emergency calls to locksmiths. And judging by the Yellow Pages or an online search, there's plenty of help nearby. For instance, in Silver Spring, Md., the telephone directory lists five locksmiths on the same street. In reality, those addresses are for a dry cleaner and four restaurants.

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A few states away, within a three-mile radius of my home, 12 locksmiths are listed online. The addresses include a school, supermarket, bank, two pizzerias and a clump of trees (that address doesn't exist). Only one is for an actual locksmith; the others may be scammers waiting to get your call.

The prevalence of fraudulent locksmiths is "a scam that is only growing," says Jim Hancock of the Associated Locksmiths of America (ALOA), whose 6,000 members must pass background checks.

Besides the thousands of honest pros (who generally charge about $100 to pick a lock), there are many more rip-off artists. In addition to phony addresses, they often have toll-free phone numbers. "The overwhelming majority of locksmiths with an 800 phone number are not legitimate," says Hancock. Typically, you're connected to a call center. You may be quoted a price as low as $15 and assured that a locksmith is en route. In reality, the pro arrives in a van with no fixed address and a scam in mind.

"The fraudsters usually say they can't open the door and need to drill or break off the lock and install a replacement," says Hancock. The work is faulty plus expensive — often $1,000 or more, and demanded in cash.

Here are some tips to help you protect yourself — and your door:

Find a reputable locksmith before you need one. — Photo by Veer

• First, find a reputable locksmith before you need one. Get references from friends and neighbors, the Better Business Bureau or at aloa.org. Log the details into your cellphone.

• Avoid any firm that answers the phone with a generic phrase such as "locksmith services" rather than with a specific company name.

• Be wary of locksmiths who arrive in unmarked cars or vans. Legitimate locksmiths usually have a van with the company name.

• Ask for an ID with name and address. (ALOA members carry a membership card and can be vetted at 214-819-9733.) Only 14 states (and some cities) require that on all service calls locksmiths carry proof that they are licensed. Those states are Alabama, California, Connecticut, Illinois, Louisiana, Nebraska, Nevada, New Jersey, North Carolina, Oklahoma, Oregon, Tennessee, Texas and Virginia. (Maryland has adopted, but not yet implemented, licensing.)

• Get a written estimate on company letterhead, with mileage charges, minimums and other fees, before work begins. Get a receipt after you pay.

• If you're told the lock has to be drilled and replaced, find another locksmith. Experienced and legitimate locksmiths can unlock almost any door.

Sid Kirchheimer is the author of Scam-Proof Your Life, published by AARP Books/Sterling.