Re: What happens if you take a sledge hammer to a weeping angel?
Supposedly,. you can't harm an angel because it's quantum locked, but that's one of the Blink details that's become fuzzy since they became a Recurring Monster. I'd theorise that - seeing as quantum decay is an inherent, unavoidable part of the nature of the universe - an Angel has to exert itself somehow to keep itself quantum-locked, and a weakened or wounded one can't do this perfectly, so it's possible to damage them...
"Some days are better than others. They say that where I come from."
"Loudly, I imagine, on the day you left."
(Blake's 7 - Rumours of Death)