Crowd control barriers (also referred to as crowd control barricades, with some versions called a French barrier or bike rack in the USA, and mills barriers in Hong Kong), are commonly used at many public events. They are frequently visible at sporting events, parades, political rallies, demonstrations, and outdoor festivals. Event organizers, venue managers, and security personnel use barricades as part of their crowd management planning.
Crowd control barriers act as a physical and psychological barrier, used to demarcate "no access" zones, and to designate space for lines. They are also used by riot police to control large gatherings.
Crowd control barricades are most commonly made of steel, although lighter-weight plastic variations are sometimes used. Barriers are most effective when they interlock, being attached to each other in a line via hooks at the side of each barricade. When barricades are interlocked, security personnel can create impenetrable lines, because such lines of barriers cannot easily be toppled over.