• The adjustment tool features a "window" in its socket so the position of the screwdriver blade holding the adjustment screw can be seen as the 12 mm jam nut is tightened (see Illustration). And the tool's unique handle pivots from one side to the other so the window is always visible. Visual contact, in addition to the feel of holding the screwdriver, allows for quicker valve adjustment because you can hold the adjustment screw exactly where you want it.