black bloc @ G20 summit

http://watch.ctv.ca/news/latest/summit-protest/#clip318869

A black bloc is a tactic for protests and marches, whereby individuals wear black clothing, scarfs, ski masks, motorcycle helmets with padding or other face-concealing items and often carry some sort of shields and truncheons.[1][2] The clothing is used to avoid being identified, and to, theoretically, appear as one large mass, promoting solidarity or creating a clear revolutionary presence.
http://en.wikipedia.org/wiki/Black_bloc