Grimrock

I think I may have found a bug... I'm in level 9/10, I found the pit where the cuirass of valor is behind a portcullis... The puzzle hint is: "Stand where the shadows cross and toss a rock with all your might to the east and north"... Seems simple enough, as there's only one square that really fits that description... So I throw the rocks but nothing happens, the portcullis doesn't open. I tried throwing the rocks east and north from pretty much every square in the room just to be sure, and still nothing happens... I checked a FAQ, and the first square I tried is supposed to be the right one. Am I missing something or is this a bug?

Thanks!

It works. You don't need to actually throw anything, just place items near the east wall and near the north wall then walk around till you step on the spot (the spot is two squares north and two squares east of the return teleporter)

Thanks a lot, finally got this to work.