This 2 Head signal is used with the Erie East Main signal w/ platform is for double track signalling. It can be used also by itself.The main Signal can also be used by itself without the left 2 Head. This signal will flip from your lefthand track placement and land on the main signal platform for double track usage. This will provide signalling for a trackage for two tracks side by side.Or be placed in the middle of 2 tracks. you can slide both signals so they are even on platform after placement. Have fun and Enjoy!!!!!!!!!! Damon