text: Tactical Control Measures
  of a forward boundary to restrict movement and fires a higher headquarters uses maneuver control measures
  and fire support coordination measures. Example control measures to use include things such as a battle
  position and a coordinated fire line. Sectors are most appropriate for any unit likely to make direct fire contact
  with the enemy during high-tempo defensive operations or when there is a fluid FLOT. Units assigned a
  sector treat areas behind the FLOT as an AO. Sectors can be further subdivided as needed into area of
  operations, sectors, or zones as appropriate. Any unit not expecting to be in direct fire contact with the enemy
  should use an area of operations or other means of terrain management. If a unit is defending in a sector and
  transitions to a hasty attack to exploit the enemy, they will continue to use the sector until an order can be
  issued that will better control the attack, which will then change it to either a zone or area of operations.
  Figure A-38 depicts a battalion sector for 1-66 Armor.
  Figure A-38. Example sector for 1-66 Armor
  DIRECT FIRE CONTROL MEASURES
  A-80. Commanders communicate to subordinates the manner, method, and time to initiate, shift, and mass
  direct fires by using direct fire control measures. The commander controls unit fires to direct the engagement
  of enemy systems and gain the greatest effect. The commander uses IPB products and reconnaissance to
  determine the most advantageous way to use direct fire control measures to mass the effects on the enemy
  and reduce friendly fire incidents from direct fire systems. The commander must understand the
  characteristics of weapon systems and available munitions (such as the danger to unprotected Soldiers when
  tanks fire discarding sabot ammunition over their heads or near them). Direct fire control measures defined
  in this publication include engagement criteria, engagement priorities, sectors of fire, TRPs, and trigger line.
  Maneuver platoon and company publications address and go into further detail on other direct fire control
  measures, such as frontal, cross, or depth fire patterns and simultaneous, alternating, or observed techniques
  of fire. Figure A-39 on page A-26 depicts common graphical direct fire control measures.