Line of sight may be partly obscured by terrain features or by other models. In such cases, the other model or unit is said to be 'in cover'. To check if a model or unit is in cover, stoop down to look from the first model's point of view:
If the other model or unit is fully visible, they are not in cover (i.e., they are 'in the open').
If up to half of the other model or unit is obscured, they are in partial cover.
If more than half of the other model or unit is obscured, they are in full cover.
The benefits of partial and full cover are discussed in more detail under the rules for shooting.