Attackers sometimes built a siege tower to scale castle walls. Soldiers lay in wait inside the structure as others wheeled it to the castle. Once there, the soldiers lowered a drawbridge at the top of the tower onto the castle wall. Some towers were almost 100 feet high, and in the siege of Kenilworth Castle, fully 200 archers and 11 catapults were crowded into a single tower.
Siege towers were difficult and time-consuming to build, however, and castle defenders could burn them down with fire arrows or firepots (launched pots filled with flaming liquids such as tar). Sometimes castle knights launched surprise raids on a tower to destroy it during construction. To protect their siege engine, attackers draped it with rawhides of mules or oxen.