Not hard enough to leave a mark, but it hurt for a good ten minutes after! She's been snappy before with strangers who stroke her - so we don't let anyone stroke her now - but never, ever with me. I am so gutted. To be fair I was leaning over her to stroke her while she was lying down on her bed but I didn't starle her and I've done exactly that a hundred times before. Behaviourist says to take her to training again to reassert who's boss. Oh, and she's a Rottweiler so it's not like it was a nip!!