Want to replace the old wall light on the patio. The plate has two round what I think are screws of some type (shown by the red arrows in the photo) that I thought I need to remove to remove the plate and everything else. Tried turning them with a pair of pliers after spraying WD-40 on them but they would not budge. Am I doing something totally wrong? Or are they stuck because of old age and I need to use something more aggressive to remove them? Thx!