This symbol is used to set up a reference to other track diagrams. During operation the Central Station can be switched to the referenced track diagram by clicking on this symbol.
Reference can be made only to track diagrams that have already been entered. You should first enter the track diagrams and then wait to build in these references until teh track diagrams have been completed.

For example, you can divide a station area into three manageable track diagrams, which each make reference to neighboring track diagrams.