He had checked out this kind of thin board online, and it was easily pliable. Patterns could be engraved on them by using a saw and a hydraulic press, and then they could be affixed to the wall as a decorative item.
In "The Lord of the Rings," their use was even greater—this was the material used for building the castles on set.
In the movie, the exterior walls of the many towering, majestic castles were made of polystyrene splint. Patterns were engraved onto them before they were fixed into suitable positions.
Then plaster would then be sprayed onto the surface, using a huge plaster machine. Lastly, polystyrene and paint would be brushed on to give the city walls a perfectly melancholic, ancient look.
