1988 Chevy S-10 Vacumn Spherical ball

I post the same question on here last week, but was told it was the charcoal cylinder for the fumes coming from my gasoline tank. This time I`ve included a photo of what I`m talking about.....no mistakes.

Could someone please tell me how to hook this little ball up, what it does, and where the lines go "to" and "from". My place where I get all my parts from tells me that it belongs to a 1988 S-10/2.5 engine, but he does not know anything else. The engine has all been redone, so there is no evidence of any daggling hoses to give me a clue. Thanks.