A collering ceremony is similar to a marriage in the BDSM community. It is a ceremony that represents a commitment of the submissive and dominant. It marks the ownership as property of the other.
More About Collaring Ceremony
During the ceremony, the submissive is lead in by a trainer or another dominant. However the sub may be joined by friends or other subs. Collaring ceremonies are highly personal. The dominant is usually accompanied by a few of their friends. One of them carries the collar that will be used to claim the submissive. If the submissive wore a training collar, it is removed during the ceremony and replaced with the new collar. During the ceremony, vows and obligations are explained and agreed upon. Usually, a contract is signed. It is similar to a ring ceremony observed by many vanilla couples.