\Safety chain\
(a) (Railroads) A normally slack chain for preventing
    excessive movement between a truck and a car body in
    sluing.
(b) An auxiliary watch chain, secured to the clothes, usually
    out of sight, to prevent stealing of the watch.
(c) A chain of sheet metal links with an elongated hole
    through each broad end, made up by doubling the first
    link on itself, slipping the next link through and
    doubling, and so on.