In the Middle Ages, before the advent of street lighting or organized police forces, fortified cities and towns used to discourage vandals by closing their gates and laying chains across their roads, “as if it were in tyme of warr.” Historian A. Roger Ekirch writes that Nuremberg “maintained more than four hundred sets [of chains]. Unwound each evening from large drums, they were strung at waist height, sometimes in two or three bands, from one side of a street to the other … [and] Paris officials in 1405 set all the city’s farriers to forging chains to cordon off not just streets but also the Seine.”

In some cities, residents who’d returned home for the night were required to give their keys to the authorities. A Paris decree of 1380 reads, “At night all houses … are to be locked and the keyes deposited with a magistrate. Nobody may then enter or leave a house unless he can give the magistrate a good reason for doing so.”

(From Jane Brox, Brilliant: The Evolution of Artificial Light, 2010.)