Related:

• Any error in any calculation will be in the direction of most harm.
  -- The RPCISPE's Second Universal Law...
• Theory of the International Society of Philosophic Engineering In any calculation, any error which can creep in will.
• In any formula, constants (especially those obtained from handbooks) are to be treated as variables.
  -- The RPCISPE's Third Universal Law...
• The most vital dimension on any drawing will probably be left off.
  -- The RPCISPE's Fifth Universal Law...
• Interchangeable parts won't. -- The RPCISPE's Eleventh Universal Law
• If only one bid can be secured on a project, the price will be unreasonable.
  -- The RPCISPE's Sixth Universal Law...
• Any typographical error will occur in the place in which it will do the most damage.
• Johnson's First Law: When any mechanical contrivance fails, it will do so at the most inconvenient possible time.