I have had the honor of attending two collaring ceremonies. 

 The first was several years ago. An old college friend invited me to a small chastity ceremony for her husband. The man of the hour brought a chastity cage to his wife on a velvet pillow. There were words and vows exchanged and the cage was locked with a 'click' that everyone in attendance heard. Then he fastened a leash to his new cock cage and presented it to his wife. Beautiful

The second, just a few weeks ago was a simple collaring. The young lady involved entered the room where we were all waiting, slowly took off her robe and knelt down. A leather collar was placed around her neck and was padlocked. She then stood up and served drinks to everyone, naked except for her collar.