Force protection is a commander's top priority in any military operation. For this reason, civil engineers must always be aware of the latest tactics, techniques, and procedures (TTPs) used to protect our forces, particularly in hostile environments. Engineers implement physical security measures to protect personnel and critical assets needed to achieve military objectives. To assist in these efforts, this handbook is intended to be a reference for constructing and employing expedient fighting positions, obstacles, shelters, and revetments. It focuses primarily upon measures engineers can employ to protect airbases and mitigate the effects of direct- and indirect-fired weapons. Topics covered include: effects of weapons types, fighting positions, concealment and camouflage, bunkers, roadblocks, concertina wire, barbed wire, bollards. Direct- and indirect-fired weapons are common threats to airbases. Direct-fired weapons are projectiles designed to penetrate exterior protection. These weapons are highly accurate and capable of firing different types of projectiles including: (1) chemical or kinetic energy projectiles, (2) ball or tracer rounds, and (3) armor piercing rounds or high explosive shaped charges. Indirect-fired weapons include mortars, artillery shells, rockets, and bombs. These types of weapons are highly mobile and easily concealed. They can be fired from launchers or set on timers to allow aggressors time to escape prior to launch. Indirect-fired weapons do not require a clear line of sight to a specific target; aggressors rely on blast and fragmentation effects to damage or destroy their intended targets.