collar
Besides the common definition, a BDSM symbol of attachment of a submissive to a Dominant through collar made of metal, leather, or other material. Similar to a wedding band in vanilla society. Most collars are equipped with rings where a leash or restrain can be attached, like a dog's collar.
Example:
Wearing his collar to sleep was uncomfortable, but it reminded John all of the time that his Mistress loved and owned him, and he felt safe.
Wearing his collar to sleep was uncomfortable, but it reminded John all of the time that his Mistress loved and owned him, and he felt safe.