When Matt Knox was selling insurance to contractors, he kept hearing many of them say they were frustrated by leftover building materials they had to store or somehow dispose of.

So Knox saw an opportunity. He started DiggersList.com, a Web site that originated as a marketplace for surplus building materials at discounted prices. But it quickly became much more: a classified advertising service where homeowners can post jobs for contractors to bid on and where handymen can advertise their services. The posting service is free; revenue will come from advertising.

“If we provide a free service people will want to use, the advertising revenue is exponentially better,” Knox said.

Knox and his brother Johnnie Munger launched their Manhattan Beach-based enterprise in October after a year of testing the site with Knox’s insurance clients.

“I would talk to my clients and say, ‘Hop on the site and say yes or no,’” he said. He dropped out of the insurance business and devoted all his time to DiggersList.

The site is divided into services for 16 cities throughout the United States. Knox plans to expand it into 224 cities within the next 12 months.

DiggersList allows people such as general contractors, architects, carpenters and painters to build a profile that details the type of work they specialize in and post photos of completed projects. The site will also add a forum where people can write reviews.

“There is a growth spot in builders making their way toward the Internet and becoming comfortable with it,” Knox said. “They are willing to take the time to create a profile and market themselves to find more work.”

Of course, it’s an open question as to whether the Web site can cut through the clutter and get the attention of consumers and advertisers, but so far, so good.

Andrea Kristy, co-owner of South Bay Handyman, began advertising her company on DiggersList a month ago. The day after she posted an ad, Kristy said she started getting more calls.

“Business has picked up,” said Kristy, whose company specializes in electrical, plumbing and flooring work. She feels her DiggersList ad has proved more effective than Pennysaver and YellowPages.com. “We are getting at least two more calls per day as a result of advertising on there.”