Like doors, you can adjust the amount a shutter is opened.
You can shoot while holding a shutter, but try not to do this if you are on your own as there is a slight delay
before you can shoot when you are vulnerable to enemy fire.
Have your squad mates cover you while you open the shutter.
Like doors, shutters can be held, and you can attack whoever's holding one using the gap at the bottom.
Please see the following for more info