The Collaborative International Dictionary of English v.0.48:

chains \chains\ (ch[=a]ns), n.
   metal shackles connected by chains, used to bind hands or
   legs; as, he was kept two weeks in chains.

   Syn: iron, irons, chain.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

chains
    n 1: metal shackles; for hands or legs [syn: irons, chains]