Start on the receiver, and continue the lines up onto the sight base. These large, sharply contrasting marks are easier to read than the notches on the base and receiver. The M16 and its many civilian clones are both easier and harder to target than the earlier designs. Targeting for elevation is simple if the rifle is equipped with the A2 type square front post with four detent notches in the flange. Each notch represents approximately 1.2 minutes of elevation change, about 2.5 inches at 200 yards.
Clockwise rotation raises point of impact.
Front sight posts that have been tapered on the sides and top to present a sharper profile should only be adjusted in full 360 degree rotations, which will result in nearly five minutes of change. Finer elevation adjustments will have to be done with a file. Windage targeting can present a problem. If the front sight base is attached to the barrel with two tapered cross pins, then no targeting is possible. You just have to hope the sight base is installed close to where it needs to be.