It was conceived in the late 1970s to jump-start a residential real estate market that had been battered by a weak economy and double-digit fixed mortgage rates.
It proved its worth during the glory days of the mid-1980s, when it provided the most exposure - and the quickest turnover - for houses in both city and suburb.
We're talking about the open house.
There are two kinds: One provides an opportunity for agents and brokers to see a new listing - often at noon at midweek, and usually with food provided. The other, of course, serves as a showcase for prospective home buyers.
Are open houses still important, or are real estate agents and consumers simply going through the motions?
"We get very few agents attending brokers' open houses in Upper Bucks County unless they have a buyer in that price range and for that type of home," said John C. Suchy, of Coldwell Banker Hearthside Real Estate in Ottsville.
Most agents say they can "see 25 pictures on the MLS system, so why should I go all over the county to see it in person," Suchy said.
Plus, he said, these days there are fewer "tire-kickers" - people whose hobby is hitting open houses.
"If they come out to see a place, it is not just because the Eagles aren't doing well," Suchy said. "They have interest."
He cited a recent open house at an $895,000 property in Erwinna that attracted two couples, "one in a Porsche and one in a spiffy BMW."
Open houses are "most beneficial to the seller, in that they don't have to continually be inconvenienced with sporadic showings and having to keep the house in pristine condition for buyers," said Carol McCann, of Re/Max Millennial in Fox Chase.
The benefit to an agent is to gain access to as many buyers as possible and get the home sold.
"There's also the opportunity to engage buyers who are not currently working with an agent, thereby enabling the agent to generate buyer and also listing leads," McCann said.
Open houses "are still helpful if the showings on a property have declined, if there has been a major price reduction, or if the property is on a busier road," said John Duffy, of Duffy Real Estate on the Main Line.
"Buyers feel that they are able to preview the home in a more casual manner without the seller being present," he said.
Marilou Buffum, of Berkshire Hathaway Home Services Fox & Roach Realtors in Chestnut Hill, said open houses "bring out people who might not even be thinking of looking at the house but will come just because it is open - and they wind up really loving it."
The open house also is a way for neighbors and friends to walk through a house and tell others about it, she said.
"It is another way to maximize exposure of a property - you need to see it to know it is there," Buffum said.
The whole notion of open houses has changed, said Mark Wade, of Berkshire Hathaway Home Services Fox & Roach Realtors in Center City.
"Up until a decade ago, they were a major marketing tool, as buyers had limited access to information about specific properties," he said. The internet has given buyers greater knowledge of the process, he noted.
Online listings of open houses "have the potential to be much larger than back in the days of the newspaper being the sole source of information," Wade said.
Because internet access to listings has empowered buyers, "we are now seeing the majority of open-house attendees already working with an agent and already prequalified, as well as much more serious and motivated about the home-buying process," said Ruth Feldman, of Weichert Realtors McCarthy Associates in Mount Airy.
The value of open houses may depend on location - say, Center City rather than Bucks County - said Martin Millner, of Coldwell Banker Heartside Real Estate in Yardley.
"I have never used open houses as a main part of my strategy," Millner said.
"In virtually every case where I have explained to sellers why I don't necessarily do Sunday open houses," he said, "the sellers' answer is usually, 'Thank goodness, we hate open houses.' "