12) Underground tunnels
Offer concealed avenues for troop movement. Infrastructure for utilities such as water and electricity often is located underground.
13) Going inside
Forces only enter buildings when absolutely necessary because of the danger it entails. An analysis should be done prior to entry, using whatever information available. A building's material is relevant because its structural integrity can be compromised by the rigors of war. Floor plans with mobility corridors are valuable, but often unavailable.
14) Surprise entry
Buildings are cleared from the top down, when possible. If forces do enter at ground level, they might demolish a wall, rather than using a door or window.
15) Marking territory
Rooms and buildings are marked with tape, spray paint or chalk as they are cleared. Markings point out safe entry points, dangerous areas or signal that a medic is needed within.
16) Concealed risk
The threat of enemy fire penetrating walls, floors and ceilings heightens risk.