The following lines were added (+) and removed (-):
Open Iron Sights provide horizontal and vertical reference points that allow the shooter to train the weapon. With typical blade iron sights, the shooter should center the front post in the notch of the rear sight and the tops of both sights should be level. Since the eye is only capable of focusing on one plane, and the rear sight, front sight, and target are all in separate planes, only one of those three planes can be in focus. The front sight should be in focus.There are a number of different types of iron sights. Each manufacturer's sight can have different methods of aligning Point of Aim (POA) and Point Of Impact (POI). Adjustable sights allow the individual users to adjust the sights to their preferences. Typical simple iron sight alignment centers the front post in the notch of the rear sight and the tops of both sights should be level with the desired POI.