Before the Janey took over the coupling task, freight cars used link & pin coupling, but many carriers used the Miller "hook" for their passenger rolling stock. Maybe the carriers with intense passenger operations may have had station switchers with the Miller's, but a railroad like the Nickel Plate did not. So, how did a yard switcher swing over from the freight lead to assemble a passenger train, or merely cut a car in or out of a consist at an intermediate point?

I believe that Miller Hooks had a slot and pin hole cast into them for this very purpose.

Looks like the link & pin provision was built in to the hook. https://www.midcontinent.org/rollingstock/dictionary/millerhook_restoration.htm

Rich C.