They are called binding posts.
I am not a prewar expert, but I believe that Lionel commonly used 4-36 screws with insulated washers to make up their binding posts.
One screw would not have any insulated washers, providing the "ground" connection for the building.
The other screw would have one plain flat insulating washer, and one shouldered insulating washer to isolate the screw from the building. The washers were arranged so the shoulder protruded into the hole, and the plain flat one went on the opposite side. The metal of the building is sandwiched between the two,