MCRP 12-10B.1, page 94

(8) The commander assigns final protective fires and machine gun final protective lines (FPLs). Machine gun positions provide interlocking grazing fire and mutual support between adjacent units. FPLs are fired on planned signals. Proposed FPLs must be “walked out” to determine the extent of grazing fire available and to locate dead space. Dead space can be covered by: Rifle and light machine gun fire Grenade launchers Mines and boobytraps Indirect fires. (9) Long-range antiarmor weapons are employed in the forward areas of the main battle area and the security area. Antiarmor weapons must be carefully positioned to prevent terrain and obstacles from reducing their range. Dismounted and manpacked antiarmor weapons should be positioned in buildings and along routes where engagement distances are reduced but where surprise and ambush are ideal. e. Logistics. Just as in the offense, the defense utilizes a greater amount of class V and class VIII supplies in the urban environment. The defender needs to plan for multiple routes and means of supply. These can include: Using the city's existing transportation infrastructure to move supplies Prepositioning supplies in the defense in depth Using helicopter assets for rapid resupply Establishing and protecting supply routes Plan for utilization of existing repair and maintenance facilities Identify potable water sources f. Force Protection (1) Employment of Engineers. Engineers are employed at the battalion level or attached to companies and integrated down to squad level. Commanders must consider and assign the priority of work for engineer tasks that enhance survivability, mobility, and countermobility. Tasks that engineers can accomplish in the defense of a built-up area include: Constructing obstacles and rubbling for countermobility Military Operations on Urbanized Terrain 3-23