AFTER two relatively mild winters, Rahm Emanuel’s ability to manage a snowstorm was put to the test earlier this month when it snowed, with little respite, for nine days. On the worst day of the storm Chicago’s mayor cancelled lessons in public schools to minimise traffic. He deployed more than 280 of the city’s salt-spreaders, asked residents to check on family, friends and neighbours, kept schools open for children who had nowhere to go and asked libraries to double as places to keep warm.

Unlike his predecessor, Richard Daley, Mr Emanuel did not mention “dibs” in his remarks about the snow, though he has in the past conceded that he believes in “sweat equity”. Dibs are a Chicago tradition that divides Chicagoans. If you shovel snow from a parking space and defend it with some old furniture to mark the space, you can claim it for as long as the city is covered in snow. “If someone spends all their time digging their car out, do not drive into that spot,” said Mr Daley in a press conference in 2000. “This is Chicago. Fair warning.”

Boston, Philadelphia and Pittsburgh have something similar. In fact it seems that snow, a population density of about 1,300 people per square mile and lots of Italian-Americans are the necessary ingredients for a dibs culture. But the unwritten rules governing dibs in Chicago are the most sophisticated.

Temporary ownership of a spot encourages locals to do the job well by scraping the snow all the way to the pavement. Chairs (mostly lawn chairs, the tattier the better) and traffic cones are the most commonly used dibs. But cut-outs of Leonardo DiCaprio, statues of saints or the Virgin Mary, giant stuffed teddy bears and sparsely dressed mannequins have also been spotted. Not acceptable as dibs are empty cereal boxes, Zimmer frames and cardboard signs with death threats (“Move this and die” is not considered midwestern nice). In Boston, by contrast, pinching a parking space shovelled by someone else may result in a menacing note on your windscreen, if you’re lucky.

This winter Havas, an advertising agency, and Lincoln Park Community Services, a charity, persuaded 20 local artists to create dibs chairs for auction on eBay, an online auctioneer, to help the homeless. One created a chair with a skull and crossbones in the shape of shovels. Another simply says “Nope” in red letters. A third appeals to gentler sentiments with a wooden bird-house resting on a branch adorned with the sign, “Please do not disturb the birds”.

City officials warned that they would start clearing “dibs chairs, cones and other objects” as the snow melted. Then it snowed again, though not enough to justify continued dibbing. Among the unwritten rules of Chicago dibs is that snow must be plentiful (more than a couple of inches) and the space shovelled must be in front of the shoveller’s house. And even though Lefty Out There, another local artist, made a chair for charity inscribed with “If you taka my space, I breaka you face”, you cannot slash the tyres or threaten someone who, wittingly or not, slides into your space anyway.