How does a ballpoint pen draw ink?

A ballpoint pen draws ink with a tiny metal ball at its tip. As you move the pen, the ball rolls in its socket, picking up thick ink from inside the pen and pressing it onto the paper in a steady line.

The ink is made thick on purpose, so it does not spill out when the pen is still. The little ball controls the flow beautifully: it blocks the ink when resting, then carries just enough forward when your hand starts writing.