TheKillerBs
Maester
Yes, that could be a very effective tactic if Hagrid gripped the shield properly, as opposed to by the edge as I believe he would. Mostly because the mental image of someone trying to keep a rabid dog at bay with a trash can lid popped up into my mind as I was reading the thread, and I'm not really married to the idea. Hagrid is smart, I'm sure he could figure out the proper way to grip a shield just by looking at it. But yes, if Gregor knew it was coming he could do some damage by sliding. However, I doubt that, without a proper stance and especially without the muscle memory of training how to cut someone's legs while he slides, he could do manage to make a cut deep enough for muscle or ligament damage unless he was really lucky on where the blade sliced.