For the keys that play the near row of jacks (closer to the player), the mechanism works like this. The portion of the key that engages the lower end of the jack is U-shaped, with each prong of the U ending in a wide, flat upper surface. (This U-shaped part is shown in blue in the false-color diagrams below.) The entire keyboard mechanism can be slightly shifted toward or away from the player, using knobs at the sides of the keyboard. Depending on the location of the keyboard, the jacks will be aligned in different ways against the U, resulting in different strings being played. The three possibilities are shown in the diagrams below, which depict sounding jacks in green, silent ones in red.