This technique involves a qualified technical access individual descending a fixed rope.  This technique is most commonly used to inspect towers or like structures where access to the top is readily available.  The inspector uses a descending device attached to his/her harness as the primary means to control the rate of descent while also having a prusik attached to a separate safety backup rope (with one end of the prusik attached to the harness).  A static rope should be used for rappels as it is designed to allow minimum stretch which enables the inspector to control his/her descent better and because the sheath of a static rope is generally better designed to handle the heat buildup of rappelling.  A Technical Access Rigger, Foreman or Supervisor shall install all rappelling anchors.