Weapons that use a template, such as a stone thrower or cannon, inflict D6 hits on any unit in a building that is touched by the template. If a building is hit by a stone thrower, these hits are resolved at the higher Strength only if the centre of the template lies over the building, otherwise the lower Strength is used instead.
For example: A building is hit by a cannonball. The unit inside suffers D6 Strength 10 hits. As the cannon has the Multiple Wounds (D6) special rule, all unsaved wounds will multiply to D6.