[![enter image description here][1]][1]  
Source: [tkaviation.net][2]

I suspect it's related to the fuel system, but it's only found on the left wing. I haven't been able to find the right keywords to find anything about it.

I'm hoping to know its function and how it does it.


  [1]: https://i.sstatic.net/ICdMY.jpg
  [2]: https://tkaviation.net/2019/02/23/for-sale-1978-c-152-ii/