safety chain

Century Dictionary and Cyclopedia

1. n. On a railway, an extra chain or coupling attached to a platform or other part of a car to prevent it from being detached in case of accident to the main coupling; a check-chain of a car-truck; a safety-link.
2. n. A short chain placed between a car-body and the truck to prevent the latter from swinging at right angles to the body in case it leaves the rails while the car is moving; a check-chain.
3. n. A light chain designed to be attached to a key-ring or watch to prevent it from being stolen from the wearer's pocket.

GNU Webster's 1913

1. (Railroads) A normally slack chain for preventing excessive movement between a truck and a car body in sluing.
2. An auxiliary watch chain, secured to the clothes, usually out of sight, to prevent stealing of the watch.
3. 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.