What you are looking at is an electrically operated valve.
The "cross feed", which is a misnomer, allows both tips to feed simultaneously no matter which tip is selected on the fuel selector if the "fuel cross feed on/off" switch is in the "on" position. In the "off" position only the tip selected on the fuel selector feeds the engine.
The fuel returns to the left main in either case.
The trouble with using the "cross feed" is that the tips never drain evenly.
In my V35B when I have burned 12 gal from one tip that returns 8 gal to the left main so it's easy to burn 16 from the left main, 12 from the right tip, 12 from the left tip, leaving, at that point, both mains full and both tips empty with 40 gal total burned. Then burn off 20 from the left main, 20 from the right etc.