Siege wespons are used in conjunction with field combat in battle situations. This requires restrictions on power or poundage of the recurve bow, and bolts of a safe design to hit men in armor. Trebuchets, ballistas, and catapults are included in this class. Here are pictures of ballistas. For more, go to http://www.sca.org/officers/marshal/combat/c_archery/ or http://www.siegetheday.info/