Since all weapons rely on their rigidity to some extent, Ogre’s Rending Grasp (the second clause of the Contracts of Stone) is particularly good at defeating them. By making metal, wood, and other materials less durable, the clause renders them less able to hold an edge and more likely to deform on striking an enemy.
In general, every success scored against a weapon reduces its damage code by 1. Bludgeoning weapons bend and deform, bladed weapons dull after a single strike, and firearms malfunction in any number of ways.
Melee weapons rely on their structure to convey force to another person. When their damage reaches 0, they automatically have a damage code of 0B. All attacks after that point deal damage to the weapon as well as to the target. Once the weapon’s Structure points are gone, it can no longer be used as a weapon at all.
Firearms need their structure to contain the explosions of gunpowder and make sure their bullets go in one direction. When a gun’s damage code reaches 0, its own bullets tear it apart. Every attack made after that point is automatically reduced to a chance die.
You can target unattended objects without hindrance, no matter what they are. Attended objects, however, are another matter. First, you suffer a -2 to activate the contract. Second, you can only target one part of the item: a knife’s blade, but not the handle; a rifle’s magazine but not its trigger, etc. Third, you must be able to see the part of the object which you want to affect. Fortunately, all weapons need their business end exposed to the target in order to function, so this is rarely a concern.