Three decades ago, Chairman Mao's government knocked down Peking's historic city wall to make way for the second ring road. Resourceful local residents spirited away some of the rubble, turning the 50lb blocks into everything from door-stops to kitchen walls and bomb-shelters.
Now, the cultural relics authorities are asking Pekingers to hand back their booty, and thousands of bricks from the old Ming city wall - more than 30,000 so far - are reappearing so that one small part of the past can be put back together again.
At the designated collection site, the bricks are arriving by bicycle, tricycle cart, and sometimes taxi. Call a hotline number, and Qi Kesun at the state-run Peking Antiquity Reconstruction Company will leap into his blue truck (its banner reading: "Love the old capital, give back the city wall") and come to pick up your bricks.
Mr Qi has developed quite an eye for Ming masonry. "These ones aren't bad!" he exclaimed after being summoned to a building site in western Peking. Chipping off ice, he showed how the stamp on the side of each brick identified the year of production and the firing kiln. Zhang Lailong, whose hovel was next in line to be demolished, said his family had long ago acquired three old bricks. "They were put under the bed to make it more stable," he said.
Mr Qi's unit is run by the Peking Cultural Relics Bureau which recently launched a plan to renovate and extend a stretch of the city wall just east of the main railway station, one of the few places where anything is left.
Even these precious remains had been set for demolition by a Sino-Dutch building project, until a sharp-eyed Chinese man working near by wrote to the local newspaper to alert people. Public sentiments were roused, the bulldozers halted, and the official call went out for the return of old bricks for the rebuilding and an associated museum project.
The Peking wall originally dated from 1267 when the conquering Mongols built a new city with earthen ramparts.
A century later, the Ming dynasty rulers built new north and south walls around a smaller settlement, and then in 1420 also encased the east and west Mongol walls with brick. The resulting structure was made up of an earthen centre up to 10 yards wide, with brick exteriors two yards thick on either side.
Anyone in Peking over 40 years old has fond memories of the wall. Michael Crook, a Briton who grew up in Peking, recalled it in the early Sixties: "On the way home from school, we used to climb up and lark about on the top of the wall. It was all very pleasantly dilapidated and overgrown with bushes and jujubes."
The demolition teams struck in 1965, when the government gave the go- ahead for the new ring road. The half-mile long stretch which is the focus of the renovation project, is the inside brick casing of one section of the former east wall.
Mr Crook, who has carefully researched the wall's history, is concerned that the few remnants are preserved rather than reconstructed. "I'm terribly worried that they might decide to restore it or renovate it, while what is really needed is protection.
"My theory is that China is still very poor, but in another 20 or 30 years the authorities would have the resources to do things properly.
"In the meantime, the less done the better, because the track record has been patchy. Some people's notion of preservation is to tear the whole thing down and rebuild with new materials."
Behind all the propaganda, the campaign for old bricks does seem to have touched a chord with the people of Peking. There have been 2,000 calls to the hotline to arrange collection, and dozens of people have struggled by themselves to deliver back the heavy slabs. The only reward for donors is a certificate.
Liu Jincai, 54, who lives near the old north-west corner of the Ming wall, took his bicycle to rescue 20 bricks from a nearby building site.
"I called the hotline almost every day. There are a huge number of old bricks at the building site. I am afraid the big machines will destroy them and take them away as rubbish."
His wife laughed: "My husband every evening asks me to go to the site to pick up the bricks. But I'm not quite that keen!"