Looking at the parts catalog here:
https://catalog3d.winnebagoind.com/menu/Parts.htm
That appears to be a threaded plug. That likely needs to use something like large channel lock pliers to grip the square part and turn counterclockwise?
Check if there are threads on the inside of the round "rim" where the plug sets down in the hole?
I "think " there will be but I've not actually seen it, so my idea needs checked.
__________________
Richard
Why no RV year, make and floorplan on MY signature as we suggest for others?
I currently DO NOT have one!
Linear Mode
