“Within one stand width” is the only measurement used in Crossfire, and is used in several places. Using official base sizes it is about 1-1/4″ from base edge to base edge, and you should “eyeball” it. But there is still some ambiguity.
Where to look in the rules
Relevant sections of the rules:
CF1.0 Prepare to Play: Figure Scale, p. 1
CF2.3 Commanders, Subsection Commander Assistance, p. 2
CF4.2 Group Movement, p. 4
CF6.4 Fire Procedures, Firegroup subsection, p. 10
CF7.1.1 Barrage Fire (HE), Kill Potential subsection, p. 13
CF8.0 Close Combat
CF11.1.2 APC Passenger Capacity, Mounting and Dismounting Passengers subsection, p. 18
Less than but not equal to a stand width
Be warned that “Within one stand width” means less than one stand width; in other words, if you can fit a stand in between, then it is too far. That means if three stands are lined up in a row with no gaps, the outside stands are beyond “one stand width” of each other. This is a clarification Arty made to the Crossfire Discussion forum.
For example, with five stands of a platoon in a tightly packed line, and with the Fire Group Leader (FGL) being the centre stand, only the middle three stands can participate in the firegroup. (Similarly if the FGL was suppressed in barrage fire, only the adjacent stands would be eligible targets for kill potential.)
“Within one Stand Width” for a Fire Group
Command and Control
Similarly for rallying and commander bonus in close combat. A PC in the middle of a tightly packed line can only provide assistance to the nearest squads.
“Within one Stand Width” for Rallying and Commander assistence
That is not to say assistance can only be offered to adjacent stands, just that there is a limit to the distance. For example, in the following diagram the PC can provide assistance to stands 1 and 3, but not 2 and 4. You’ll notice that stand 2 is exactly one stand width from the PC (being on the other side of stand 1), and stand 3 is fraction closer.
Mounting / Dismounting APCs
And the same principle applies to mounting/dismounting to/from APCs. In the example the PC and Squads 1 and 3 can mount the APC, but squads 2 and 4 cannot.
“Within one Stand Width” for mounting/dismounting APCs