Building a stone castle was an epic endeavour, recquiring a great deal of manual labour. Special devices were used to heip lift large stones. In medieval manuscripts there are dozens of images depticting such stone-lifting devices. These images have served to recreate two replicas - a crane and a tripod hoist stand equipped with several pulley blocks.
Siege engines such as the trebuchet - one of the top choices for artillery in ancient and medieval warfare, having the ability to throw heavier projectiles farther and more precicely than earlier catapults could - or the mangonel. The mangonel was developed by the Romans. It was powered by tension created by twisted ropes like the ballista, but had only one arm instead of two. The advantage of this catapult was that it was very light and its ability to throw rock and fire. The major disadvantage was that it was not that accurate. The range was determined by the weight of the projectile and the strength of the mangonel. In order to get the catapult into effective range of a castle, it would have to come into range of the castle's defenders.