SunPro Fuel Gauge? HELP!

So I'm wiring up my fuel gauge in my 58 Chevy and i was wondering what connects to the "s" post on the back. It has 3 posts, one +, one -, and the s posts. Any help would be appreciated.

Thanks,
-Cam.

 

just a wild guess....sender

 

The S post connects to the post on top of the sender mounted on top of your fuel tank. Make sure the sender housing is grounded or it will read full all the time.

 

awesome, thanks.