Looking at youtube they show a video on how to adjust a Corolla headlamp for up to the year 2001 and then another video onwards from 2003.
My Corolla is 2002 and does not have the set up either of these videos show. Which i think might be from the USA and so not applicable for me in the UK.
I'm guessing here, but could it be a plastic allen key socket, which looks like it could clamp down on something like a plastic Rod. That i could then slide? I'm well in the dark with this. Grateful for any advice.