San Francisco is using boulders to discourage homeless people from camping under some overpasses, according to the Chronicle.
So far, the Department of Public Works has put boulders in an area known as "the Hairball" -- at Cesar Chavez Street and Potrero avenue.
Officials say, more boulders are on the way -- and may be install over the next month.
A homeless advocate is criticizing the move -- comparing the boulders to anti-homeless spikes being installed in London. Similar strategies have also been criticized in San Diego and Seattle.