That device requiring the most service will be least accessable.

Related:

• Actual service conditions cannot be met in the laboratory.
  The RPCISPE's Fourth Universal...
• Specified Service Conditions will be exceeded. --
  The RPCISPE's Sixteenth Universal...
• The most vital dimension on any drawing will probably be left off.
  The RPCISPE's Fifth Universal...
• Any error in any calculation will be in the direction of most harm.
  The RPCISPE's Second Universal...
• Interchangeable parts won't. --
  The RPCISPE's Eleventh Universal...
• If, in engineering practice, a safety factor is set through service experience at an ultimate value,
  an ingenious idiot will promptly calculate a method...
• Operation instructions shipped with the unit will be discarded by Receiving.
  The RPCISPE's Fourteenth Universal...
• Parts that cannot be assembled incorrectly will be.
  The RPCISPE's Tenth Universal...
• Warrantee and guarantee clauses are voided by payment of the invoice.
  The RPCISPE's Twentieth Universal...