Here are filling instructions for "Aerometric Filling" fountain pens, including Parker 51, 21 and 45 pens. 1) Remove cap. 2) Unscrew barrel. 3) Place entire nib and half the section into the ink. With the nib immersed in the ink, press the bar 4 times. 4) Remove pen nib from ink and replace barrel. Hold absorbent tissue around the nib for several seconds to take up excess ink. Replace cap when not in use.