Double Vertical Line Meaning

Example: Used other than as an idiom: see double,‎ vertical,‎ line.
2007, K. David Harrison, When Languages Die:The Extinction of the World's Languages and the Erosion of Human Knowledge, page 39:
  The ǁGana people (800 speakers—the double vertical line denotes a click sound) of Botswana have no generic word for living things, nor do they recognize a plant versus animal distinction.
2008, Ursula Goldenbaum, ‎Douglas Jesseph, Infinitesimal Differences: Controversies between Leibniz and his Contemporaries (ISBN 3110211866), page 86:
  In addition, Leibniz drew a double vertical line from line 36 to 37 (from “solidum est” to “Mechanice”[)].
The typographical character ‖; a symbol composed of two closely spaced line-height vertical lines.
1998, Burkhard Dretzke, Modern British and American English Prononunciation: A Basic Textbook, page 89:
  The whole tone unit stands between a double vertical line (double bars)