Rail joiners are small clips that join two sections of track. They come in both metal, to connect the rails electrically, and plastic to insulate and isolate the two sections of track electrically. Terminal joiners are metal rail joiners with wires attached that allow electricity to flow from the power pack to the rails.The code of a piece of track is the height of the rail in thousandths of an inch. Code 83 rail is .083 inches high whereas Code 100 rail is .100 inches high. Atlas Code 83 has finer ties and rail than Code 100, making it more true to scale. Its brown ties are more prototypical than Code 100's black ties.