The warm air leaving the building simultaneously inflates and heats the double membrane structure. At the time, the city of Cambridge had made a series of vents in Harvard Square "homeless-proof" by tilting the metal grates, making them virtually impossible to sleep on.
He lists a series of these hindrances throughout the city. Such bumproof benches are being widely introduced on the periphery of Skid Row. Another invention, worthy of the Grand Guignol, is the aggressive deployment of outdoor sprinklers. To ensure that the park was not used for sleeping - that is to say, to guarantee that it was mainly utilized for drug dealing and prostitution - the city installed an elaborate overhead sprinkler system programmed to drench unsuspecting sleepers at random during the night.
The system was immediately copied by some local businessmen in order to drive the homeless away from adjacent public sidewalks.
Meanwhile restaurants and markets have responded to the homeless by building ornate enclosures to protect their refuse.
The intake tube can be expanded or tightened to fit the aperture of the vent through an adjustable lip made possible by elastic draw-strings. Hooks are attached to the metal louvers for reinforcement. All were built using temporary materials that were readily available on the streets, such as plastic bags and tape. While these shelters were being used, they functioned not only as a temporary place of retreat, but also as a station of dissent and empowerment; many of the homeless users regarded their shelters as a protest device, and would even shout slogans like "We beat you Uncle Sam!
