A tool used in some tactical operations is the planning/implementation/use of what are called “phase lines”.
Typically used on planned operations where you are orchestrating movement of persons, groups of persons, vehicles, or even entire armies; phase lines are used as markers that signal a change or a necessary action that is supposed to occur. They represent a demarcation where you enter a different “phase” of your mission.
In military operations, crossing a “phase line” (many times a physical “line” like a road, stream or other landmark) may mean that your Rules Of Engagement (ROE) have changed. A military unit may acquire different priority for artillery fire or fires may shift as units cross a “phase line”.
A fairly common use of this principle in “small-scale tactics” is using a phase line technique to orchestrate SWAT operations. While the labels may vary, many SWAT units use a “Phase Line Yellow” and a “Phase Line Green”. Phase Line Yellow represents your last point of cover and/or concealment before moving up to your assault position. Specific preparatory and communication-check tasks are performed here before moving up to “Phase Line Green”. When the order is given to move to Phase Line Green you are “at the door” and ready to start your “tactical dance” . Breachers move into position, gas launchers are readied for deployment, “tap up and tap backs” occur, weapon safeties may be disengaged etc. When you are ready to roll, the commander then gives the order to “execute”
While not particularly useful for “routine” operations; if you have a situation where you have the time to plan, and the need to co-ordinate many activities and/or persons, “phase lines” can be a useful tool.