What are these for?

[Sauerkraut]

Another simple question. When I bought the bike there was carb boots with connections on them, one was capped off and I believe the other was going to the gas tank. I searched but can't find a definitive answer. What are the prongs on the carb boots for/where do they go? Should I T them to the secondary line off the petcock? Thanks

 

[BBS360]

The line to the petcock activates the stock vacuum petcock when the engine is running.
If you're running the stock petcock it won't run without the hose to the barb.

No reason to T them.

If you have a manual petcock plug them both.

They're also used to sync the carbs with a sync tool or manometer.