Plug in wing-root vent?

[JamesC]

Took a look at the service manual - in that area of the wing the only thing there really is the plumbing for the boots - my guess is that the plug is an access port for this area but you would really have to speak to a 337 A & P to be certain. I could not find explicit mention of the plug in the service or parts sections of the manuals. My acft has two plugs (and no air conditioning). Can you feel or see anything in there ?