21.   Police, holding plastic shields interlocked in front of them and occasionally firing tear gas, blocked students from marching into the streets.

22.   Peering through thick helmet visors, a row of riot officers stood silent as student protesters prodded their plastic shields with sticks and hurled taunts.

23.   Plastic shields now surround pipes where condensation forms.

24.   Acrid white tear gas wafted in the air as masked demonstrators scrambled and fled the rifle-toting riot police as they fired from behind plastic shields.

25.   Anti-riot officers with clubs, reinforced plastic shields and rifles guarded the local Parliament building, a frequent target of pro-independence rallies.

26.   Anti-riot police officers with clubs, reinforced plastic shields and rifles guarded the local Parliament building, a frequent target of pro-independence rallies.

27.   Armed with plastic shields and batons, thousands of helmeted riot police stood guard outside the plants for possible clashes between the two sides.

28.   At one point, angry officers used plastic shields to smash the windows of a van owned by the labor group.

29.   At the end of the ceremony, students burned plastic shields they had seized from riot police.

30.   Corinthians coach Wanderley Luxemburgo, who also is manager of the Brazilian national team, took the field protected by the plastic shields of police riot troopers.