it's a nkurled knob, kinda hard to get to esp if ya got big hands. look again and make sure, turn with the hand not a screwdriver.
theres two on each bottom and side.
may have to remove a few parts to get in there, or, get the wife,sig other, etc to help.
hope i'm not talking down to ya, but it really is tight in there, and sound like your not turning the right thing.
of course i've been very wrong before
