Not sure what mirror you have, but there should be two allen screws in the round mirror bottom where it meets the arm. Those two allens let you adjust the angle of the mirror head, side to side and front to rear.
You've located that chrome cap on the base of the mirror and it needs to be removed. It has to be pried off, so try some plastic pry bars and if that doesn't work, you'll need to carefully remove it with a small flat screwdriver. Once it's off, there is a bolt inside that needs to be loosen. I forgot the size, but it requires a socket. Loosen it a turn or two, but do not remove it. It tightens down a wedge shaped arm inside. Even though you get the bolt loose, you have to wack the mirror arm with your palm to get that wedge to loosen.
Once you get it loose, move the arm to where you would like it and then adjust the head. You may need to adjust both several times to get everything even. Since the head can turn in any direction, I like to get the mirror head close to where I want it and then make sure the mirror glass is centered in the head, when I have the glass adjusted where I want it. This may take several tries, but once done, it's forever.
When I set up my mirrors, I imagine a string line running the length of the coach (up against the sidewall) and out past the mirror. I then adjust the mirror so the inner edge of the mirror head just protrudes farther out than the side of the coach, touching that imaginary string line. This keeps the mirrors in tight, yet gives you a good view.
Here are the instructions...…
https://docs.wixstatic.com/ugd/9e24a...e28be86e4d.pdf
Thor ARIA 4000 mirrors
Linear Mode
