They're for energizing the frogs if you need to, ( if locos stall going through the switch). I have had no problems with stalling, so mine are dead. If you're running older steamers with pick-up only from one side of the drivers and one side of the tender, you will probably have to hook them up.
Jay
C-415 Build: https://imageshack.com/a/tShC/1
Other builds: https://imageshack.com/my/albums
Got a Peco 3 way switch,question is there was no instructions in the box,I take it the 2 brass wires that are long and attatched get hooked up to power?