A type of heavy siege engine which hurled stones at castles with the effect of modern shrapnel. Trebuchet was the largest of the petrariae, or siege engines. It consisted of a long beam, up to 50 ft long, with massive weights of 8-9 tons at one end. It rested on a crossbeam and the long arm was hauled down by a rope attached to the end and wound on to the windlass.