Complex sentence: Angled chutes called were also set at numerous points in the castle walls, enabling stones or boiling oil to be poured on the heads of attackers passing by underneath, and white plaster was used in the castle's construction for its resistance to fire.
Split into simpler sentences: Angled chutes called were also set at numerous points in the castle walls, enabling stones or boiling oil to be poured on the heads of attackers passing by underneath. White plaster was used in the castle's construction for its resistance to fire.