Perfect and Optimal Rulers

A judicious artist will use his eye, but he will trust only to his rule.

Generating and counting perfect rulers.

• What is a perfect ruler? A short introduction.
  In English, in German, in French and in Russian.
  
  
• The basic definitions: Rulers which are complete can have
  nice properties like being length-maximal or marker-minimal.
  A more formal description.
  
  
• Counting rulers: All checked values known.
  Here is a table, some samples and the perfect ruler pyramid
  and all optimal rulers with length <= 101.
  
  
• Generating rulers: Ruler hacking is hard!
  A coder's starter kit in C#, a Sage worksheet and a
  Maple worksheet. 'Rulez', a Java program for the fast
  generation of perfect and optimal rulers.
  'Kamm', an alternative program by Klaus Nagel in C,
  here adapted to Java. A Fortran program by
  Hugo Pfoertner for complete rulers.
   
• Wichmann rulers: A great idea to find big rulers. Here
  used for searching optimal rulers with length > 1000.
  A table and insights from a discussion on de.sci.mathematik.
  Are optimal rulers Wichmann rulers? A conjecture.
  
  
• Fun! How to craft a perfect ruler by hand.
  A Java applet by Klaus Nagel.
  
  
• References to the Online Encyclopedia of Integer Sequences.
  An overview. Thanks to Hugo Pfoertner for his helpful comments.
  And to Rainer Rosenthal for many encouraging comments.