All models are part of a unit. A unit is either a group of models deployed in a formation consisting of ranks (along the width of the unit) and files (along the length of the unit) or a single model operating on its own.
When forming a unit, all models in the unit must be perfectly aligned in base contact with each other and face the same direction. Models in a unit that are not in the first rank must be positioned so that another model is directly in front of them, which means that their entire Front Facing has to be in physical base contact with models in front of them.
All ranks must always have the same width, except the rear rank which can be shorter than the other ranks. Note that it's perfectly fine for the rear rank to have gaps in it, as long as the models are aligned with those of the other ranks. A rank in which one or more models are missing is called an incomplete rank.
Following these rules, you are free to field your units in whatever formation, as few or as many files wide as you wish, but this may affect rules that interact with the unit (see full_ranks full_ranks and line_formation line_formation for examples).
Whenever a rule, ability, spell, and so on affects a unit, all models in the unit are affected.
Rank-and-File
Normal models in a unit are called Rank-and-File models (R&F). All models except Characters are R&F models.
Full Ranks
The Height of a unit determines how many models are needed in a rank in order to form a Full Rank (see ). Units of Standard Height need 5 models, Large units need 3 models, and Gigantic units need 1 model.
Close Formation & Line Formation
Units are normally considered to be in Close Formation. Units in ranks of 8 or more models are instead considered to be in Line Formation. Units in Line Formation gain the Fight in Extra Rank Attack Attribute, but don't have any Rank Bonus (see and for details on the formations' in-game effects).
Health Pools
All Health Points of a unit are part of one or more Health Pools. The Health Points of all non-Champion R&F models of a unit form a separate Health Pool, while the Champion and each Character joined to the unit each have their own Health Pool (see Champion and Characters).
Unit Boundary
A Unit Boundary is an imaginary rectangle around the outer edges of the unit. The Unit Boundary of units composed of models on round bases is identical to the area occupied by their bases (this means that their Unit Boundaries are not a rectangle but a circle).
A unit usually cannot be inside another Unit Boundary, unless the units are overlapping (see figure figure/arcs and ).
For the purpose of drawing Line of Sight to a Unit Boundary and determining if its unit benefits from Cover, the Height of the Unit Boundary corresponds to its unit's Height (see ; Model Rules such as Skirmisher, Tall, or Towering Presence can affect this).
Centre of Unit
A unit's Centre is the centre of its Unit Boundary (see figure figure/arcs).
Unit Facings
A unit has 4 Facings: Front, Rear, and two Flanks. The Facings are the edges of the Unit Boundary (see figure figure/arcs). Units on round bases have a single Facing, which is considered to be their Front Facing.
Unit Arcs
A unit has 4 Arcs: Front, Rear, Left Flank, and Right Flank. Each Arc is determined by extending a straight line from the corners of the Unit Boundary, in a 135 angle from the unit's Facings (see figure figure/arcs). Any object at least touching the line that separates two Arcs (even if only in a single point) is considered to be inside those Arcs. For rules purposes, units on round bases have a single 360 Arc all around, which is considered to be their Front Arc.
Many rules require the players to determine which Arc of a unit another object is Located in. Note that for rules purposes there is a difference between being inside an Arc as described above and being Located in an Arc (see figure figure/located_in_an_arc):
• Models/units on rectangular bases are Located in the Arc which the centre of their Front Facing is in.
• Models/units on round bases are Located in the Arc which the centre of their base is in.
• Any other object is Located in the Arc which its centre is in.
If an object is Located exactly in two Arcs of a unit, it is considered to be Located in the unit's Flank Arc.
Rank Bonus
Units in Close Formation have a Rank Bonus of 1 for each Full Rank after the first, up to a maximum Rank Bonus of 3. Units in Line Formation always have a Rank Bonus of 0.
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Unit Arcs, Unit Facings, and Unit Boundaries.
a) This unit has 3 ranks and 6 files. The base on the side is a Character with a Mismatching Base that has joined the unit (see ). The rear rank is incomplete and only contains 3 models.
The Front, Flank, and Rear Arcs are defined by drawing lines from the corners of the Unit Boundary in a 135 angle from the unit's Facings.\
b) The Unit Boundary is the area drawn around the outer edges of the unit (grey area). The Centre of the unit is the centre of the Unit Boundary (red x).
c) A Unit Boundary cannot be inside another Unit Boundary, not even with parts that aren't occupied by any models.
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Units inside and Located in another unit's Arc.Unit B is both inside unit A's Flank and Rear Arc. It is Located in unit A's Flank Arc (since this is where the centre of its round base is).
Unit C is inside unit A's Front Arc. It is also Located in unit A's Front Arc.
Unit D is both inside unit A's Front Arc and Flank Arc. It is Located in unit A's Flank Arc (since this is where the centre of its Front Facing is).
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Interaction between objects.