Law Enforcement is an unpredictable line of business. Officers often deal with persons in mental crisis, true predatory criminals with strong incentives to avoid capture, and occasionally persons who fit both of those descriptions. The presence of a firearm in a situation is no longer an exceptional circumstance.
Law enforcement training has become more centered on de-escalation when possible and upon maximizing officer safety whenever possible. Ballistic cover (something that will stop a bullet) supports both of those principles. One of the most useful tools to emerge in law enforcement in recent years is the ballistic shield.
Ballistic shields, like the shield a knight used to carry in a medieval battle, are designed to protect the bearer from harm, in this case bullets. They have proven to be invaluable assets in a range of situations such as active shooters, high risk car stops, search warrants, and safely wounded suspects following gunfights.
Ballistic shields are manufactured in two primary configurations. The most common is a shield rated to stop most rounds fired from a pistol. It is usually somewhat smaller, more maneuverable, and lighter.
The other common design is a shield rated to stop most rifle rounds. These tend to be large and heavy.