Нашёл кое-что, касаемого вашего вопроса. 95 стр.
The advantage of being on top of battlements is that the whole
unit is likely to be able to shoot - battlements do not have
Fire Points and use the normal rules for line of sight.
However, unlike those within buildings,units on battlements
can be shot back at, and will have to rely on their armour (and
any cover save from the battlement walls) for protection. Units
on battlements are not Fearless like other embarked units.
Вполне подходит под описание поверхности Скайшилда. 104 стр. По ВИЗИВИГу эти стены явно стены (ИМХО, спорить, что это деревья, окоп или дикая изгородь - маразм), насчёт которых в рульбуке есть определение.
Barricades and Walls
Barricades and walls are hastily assembled obstacles or the remains
of once proud structure;
If a model is in cover behind a barricade or wall, it has a4+
cover save. For the purposes of charge moves, models that are
both in base contact with a barricade and within 2" of each