A tournament winners banner. At this tournament, teams SLO, OLD, and MOD were all represented.
A clan tag or team jacket is a three letter prefix to a username to signify that someone is a member of a teams. The tag is usually in all capital letters and followed by an underscore. For example, if fictional user "Monstertrucker" was to join Team OLD, his new username would be "OLD_Monstertrucker."
Donning a teams clan tag is a requirement for joining any team.