Horizontal position controls the side to side position of the display relative to the physical screen area. Use this control if the right or left edge of the display is beyond the physical edge of the screen and there is a black band at the opposite edge. You may have to use this control in conjunction with the horizontal size to center and size the display on the monitor screen. Tilt controls the angular relationship between the display and the monitor screen. Adjust this control so the bottom edge of the display is parallel with the bottom edge of the monitor screen.
Pincushion controls the straightness of the side edges of the display.
Adjust until the sides are as straight as possible. This button demagnetizes the screen. Modern color monitors do this automatically when they are turned on, so this button is usually left alone. If the monitor's color balance is off, the use of this button may restore it. The display area may also need resizing as well.