Typically these safety chains are attached to the center sill frame members. There were two chains of three links on each car end. One hung on either side of the coupler. One -- the right hand chain when facing the coupler -- would have a hook on it; this for connecting the chains together between the cars. These were used on passenger cars through the steel, heavy-weight era.
Below is a photo from the Denver Public Library Digital Collection showing the end of an observation car that clearly shows the chains.
Brain Norden