Transmission filler plug Help Needed

["The Browns" <thebrown@domain.elided>]

I have a problem with my Stag.  I need to check the oil level.  How do you
get the filler plug out of a transmission which will not move with an open
end wrench?  There is not enough access room to use a visegrip as well as a
lower stiffening web that prevents getting a good grip on the square plug
surface.  Why didn't they use a hex head, so that you could use a socket?

Darwin Brown
1971 Stag
1965 TR4