In lieu of a
21 gun salute (i.e. lack of firearms and ammo)
the 21 beer salute is sometimes performed by the bros of a fallen comrade. A group of seven bros shotgun three beers each. 7 times 3 equals 21, thus the name
21 beer salute.
When the crew lost Chad
the bros gathered to pay their respects to their fallen bro by performing
the 21 beer
salute. they then proceeded to get kicked out of the wedding reception by security for partying too hard.