SCROLL BOX
                                  ══════════════↕
                            Scroll box ─────┐   ═
                                            │   ┴
Use the scroll box to move quickly to an    │   ↑
approximate location in a document. Drag    └──►█
the scroll box to the relative position         ▒
you want.                                       ▒
 
For example, to move to the end of a document,
drag the scroll box to the bottom of the scroll
bar. To move to the approximate center of a
document, drag the scroll box halfway down the
scroll bar.