Radiator covers - how to change heat setting?

[F33lguilty]

Hi,
The previous owner installed radiator covers over what looks like a fairly modern radiator. Sadly it doesn't heat up well and I need to have someone look at it. But first I want to check that it's at the highest setting on the valve.
Are these covers supposed to be accessible for maintenance etc ?
I've tried shining lights inside and the lid seems to be screwed down.
All ideas welcome!!

Can you post a photo of it? Most radiator covers I've had attach to the walls with screws. You might be able to lift it up and off for access?

The one we had at our old place just slid up and off and then back on again and was on fittings that made this possible!

Sometimes the grille over the front is removable - you push it in then manoeuvre it out and the frame, including the shelf on the top, is screwed to the wall. I hate radiator covers.

Quick update as I am very grateful for any replies on what is a dull subject!
Using a torch and camera on a timer, I can see the screws that are holding the back of the unit to the wall. Sadly that means we can't slide up and off like we can with other covers in the house.
So I need to get a screwdriver with an extension to 9 inches!
The people who lived here before did some very peculiar things..
@wowfudge I hate them too as they hamper heat transmission so much. I'm keen to get them off.