In music notation, a ledger line is a short horizontal line drawn just above or below the staff and parallel to it. The purpose of a ledger line is to indicate the pitch of a note which is outside the range of the staff, by representing a sixth (or seventh or eighth or more) line at the top or bottom of the staff.

Ledger lines look something like this, here used to indicate a pair of half notes at high C and middle C:

    /\                   |
---| /-------------------|---------------------------------
|  |  |                           
 \ |  |                         |
   |                            |
  \|                          -O--

If many ledger lines are required for more than one or two notes, an octave symbol may be used instead to make it easier to read.