It once was standard practice to have a pair of safety chains between passenger cars -- both sg and ng. Each end of each passenger car would have two chains, one of which would have a hook to connect with the hook-less chain of the coupled car.
One of my favorite cars --
And here is a Denver Public Library image of a sg Colorado Midland obs car with chains:
http://digital.denverlibrary.org/cdm/ref/collection/p15330coll21/id/3404
Heer is a view of the D&RGW car "Glenwood Canyon" on the end of a Panoramic Special.
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digital.denverlibrary.org]
BN