Universal Rule.
When deploying the unit, you may place a Wall Terrain Feature fully within 1″ of the unit’s Front Facing but not in contact with any other Terrain Feature except Open Terrain. This Wall is up to 20 mm deep, and its length cannot be wider than the unit, to a maximum of 12″. It follows the normal rules for Walls, with the exception that it contributes to Soft Cover instead of Hard Cover