Beginner Question

[robertos]

I have a 4 stroke Craftman's lawn mover and after having troubles I removed the "container"
which holds the floater of the carburetor.( to clean it )

The bolt to remove shows a tiny sort of "extension" with a small diameter hole going across it.
I cannot figure out what the purpose of this hole is as it is not connected to anything and
would appreciate if anybody can help me.

 

[Rivets]

That is the main jet. Clean it and make sure that the hole going down through the middle and side to side are open, then reinstall.