The previous poster was right in his description, it is a screw that is hard
to get to.

I have tightened the screws on both of my vent windows with what is probably
the smallest size vice grip (about six inches long).  Once you find the
screw and figure out how to get the vice grips tightly on the screw head it
is an easy process and only takes a minute or so to tighten and adjust the
windows.

Jonathan Poole
'82 ac westy