A bouncer (also known as a doorman, door supervisor or cooler) is an informal term for a type of security guard, employed at venues such as bars, nightclubs or concerts to provide security, check legal age, to refuse entry for intoxication, aggressive behavior or non-compliance with statutory or establishment rules. Bouncers are often required where crowd size, clientele or alcohol consumption may make arguments or fights a possibility, or where the threat or presence of criminal gang activity is high.