In 2005, the now defunct Rebar placed coins in a San Francisco parking meter not to park a car but to erect a small public park. Every third Friday in September since then, activists worldwide who wish to foster a conversation about the lack of public space have been transforming parking spaces into everything from greenery to art installations to places for wedding ceremonies. This September 18th, potential participants are encouraged to download the Parking Day Manifesto, which is a how-to-guide on transforming that slab of asphalt into an engaging public space.