text: Chapter 17
  * Defense. Protective obstacles provide friendly forces with local, close-in protection. They prevent
  the enemy from delivering a surprise assault from areas close to a position and are integrated with
  FPFs to defeat the final assault of the enemy. Protective obstacles are employed to defeat mounted
  and dismounted threats.
  * Security. Protective obstacles are used to prevent or mitigate hostile actions against friendly forces
  and critical fixed sites (such as air facilities, bases or base camps, critical infrastructure, and
  sustainment sites). Protective obstacles used for security produce scalable effects that range from
  lethal to nonlethal and are appropriate for the situation based on the ROE.
  17-17. Protective obstacles are key enablers to survivability operations, physical security, and antiterrorism.
  Units on the move rely on rapidly emplaced protective obstacles that units can quickly recover, deactivate,
  or destroy. Stationary units continuously improve their security posture. (See ADP 3-37 for more information
  on the use of obstacles in supporting protection tasks that are not considered countermobility tasks.)
  OBSTACLE INTENT
  17-18. Obstacle intent describes how obstacles support the commander’s concept of operations. Obstacle
  intent consists of the—
  * Target.
  * Effect.
  * Relative location.
  TARGET
  17-19. The target is the enemy force that the commander wants to affect with tactical obstacles. The
  commander usually identifies the target in terms of the enemy size and type, the echelon, the avenue of
  approach, or a combination of these things.
  EFFECT
  17-20. Tactical obstacles and fires—direct and indirect—manipulate the enemy in a way that supports the
  commander’s intent and scheme of movement and maneuver (or scheme of maneuver). Obstacle effect
  describes the effect that the commander wants the obstacles, combined with fires, to have on the enemy. The
  obstacle effect—
  * Drives integration.
  * Focuses subordinate fires.
  * Focuses obstacle effort.
  * Multiplies firepower effects.
  17-21. It is important to remember that obstacle effects occur because of the combined effects of fires and
  obstacles, rather than from obstacles alone. Tactical obstacles produce one of the following effects (see
  paragraphs 17-24 through 17-45 for protective obstacle effects):
  * Block.
  * Disrupt.
  * Fix.
  * Turn.
  17-22. Each obstacle effect is graphically represented by an obstacle effect symbol, as shown in table 17-1.
  Obstacle effect symbols are used as control measures for obstacle groups and as elements of the control
  measures for obstacle zones and belts. During COA development, obstacle effect symbols are also used in
  developing and showing the initial obstacle plan that supports each COA.