Walter A. Sheaffer filed a patent for a fountain pen design as early as 1908. Most Sheaffer pens use a plunger mechanism, and this includes the Sheaffer Snorkel pen---renowned as the most complicated mass-production fountain pen ever made. When your Sheaffer fountain pen starts to run dry, get out your favourite colour and fill 'er up.
Remove the fountain pen cap to expose the nib and feed assembly. Remove the cover at the other end of the barrel to expose the filling mechanism. If you have a Sheaffer Snorkel pen, turn the end knob counterclockwise to extend the filler tube at the tip. Pull out the plunger shaft to engage the filling mechanism.
Open a bottle of fountain pen ink. Dip the pen's nib and feed assembly or snorkel filler tube, if you have one, into the ink. Press all the way in on the plunger and then release it. Leave the pen in the ink for at least 10 seconds to allow the pen's ink sack to fill.
Lift the pen out of the ink and wipe the nib or snorkel with a tissue to remove excess ink. Be careful not to leave any paper fibres on the pen. Twist the end knob clockwise to retract a snorkel. Put the cover back on the end of the barrel.
Write with the pen to test the ink flow. When finished, replace the cap and store the pen upright with the nib end pointing up.
Be gentle with the plunger mechanism to avoid stressing the internal parts. Occasionally lubricate the plunger with 100 per cent silicone grease that contains no petroleum, which can damage the plastic used in fountain pens.