riot

lower, raise
be armed with, be equipped with, carry, have, hold
act as
The car had acted as a shield, protecting him from the blast.

behind a/the shield
a row of police officers behind their riot shields

on a/the shield
She did not recognize the coat of arms on his shield.

defensive, protective
human
missile-defence/missile-defense, nuclear
heat, radiation, wind (usually windshield)
The nose of the space capsule is protected by a heat shield.

face, gum (usually gumshield)

use sb/sth as
They used 400 hostages as human shields.

form
provide
The software provides a shield against hackers, worms and viruses.

penetrate

protect
A face shield protects your eyes from harmful chemicals.

shield against
The ozone layer forms a shield against harmful solar rays.