Not sure what the thing is called, but I saw one on here a month or so ago. It is a plastic piece that attaches to the scope just in front of the rear eyepiece, it extends out and blocks the downrange vision of one eye. I know it is best to shoot with both eyes open, and I have always done that with shotgun/pistol/open sights....but with the scope my left eye does not like to behave so I want to experiment with something like I've described here. Any help is appreciated.