Piecemaker allows total destruction of the game worlds items, meaning walls will be totally destroyed in how they where (Like a Catapault shot skimming the top would take the battlements out for example)
Here is just a little test demonstrating what it can do for small items, note this how it would of broken.
It's "would have" not "would of"
What sounds like an of in speech is from the abbreviation "would've"