noun (n)

• a person who fastens or makes fast(noun.person)

  Example:
  He found the door fastened and wondered who the fastener was.
  

  source: wordnet30
• restraint that attaches to something or holds something in place(noun.artifact)

  Synonym:
  fastening, fixing, holdfast
  

  source: wordnet30
• One who, or that which, makes fast or firm.(noun)

  source: webster1913