The interesting thing about blindspots is that they are so well camouflaged that we are very seldom aware of them. It's especially hard to notice their edges.
You might be aware that you do not have eyes in the back of your head, and so you have quite a large blind spot whenever you are in the middle of something. You might even be aware that your peripheral vision is a bit blurry and your foveal (focused) vision is a bit slow - so that you catch movement best out of the corner of your eye and edges best straight on. So you know that what you see clearly is not even close to the whole picture. You have to make mental adjustments in order to live in a world with nicely defined edges.
What you cannot notice - except theoretically - is that you also regularly create visual information to replace information that should be there but is not. There are places (one per eye) in your field of vision that you cannot see because of the way your eye and brain process information. This is not a problem for your brain: it sees all around the blindspot and fills in the missing information with what it believes should be there. It fills in your blindspot, continuously and effortlessly, whenever your eyes are open.
You never realize that you are missing information.
Unless someone else is present. Someone else who is viewing the world from a different position. Someone else who has a different blind spot.