At some events, security guards and police use metal detectors and sniffer dogs to prevent weapons and drugs being brought into a venue.
A common method of crowd control is to use high visibility fencing to divert and corral pedestrian traffic to safety when there is any potential threat for danger.
[8] Keeping the crowd comfortable and relaxed is also essential, so things like awnings, cooling fans (in hot weather), and entertainment are sometimes used as well.
Thus, restrictive measures and the application of force can actually make crowding more dangerous, for instance during the Hillsborough disaster.
Their job is to simply hold the crowd back, which would end in a free for all and resulting in multiple officer injuries.