LOL, I don’t even know what that is!
From a time when we left doors unlocked.
In case you really don't know what that was it is a card that you placed in your screen door so the Ice Man knew how much ice to chip of the big block and place in your Ice Box. No one needed to be present for that to happen. Happier times for me in those days, when an ice chip was almost as good as ice cream.