This is the forum for helping you out if you're stuck or if you want to discuss the nitty gritty details of the dungeons within Mount Grimrock. Warning: forum contains spoilers!
You should have already found it to get through an iron gate. Assuming you didn't pick it back up it will be in an alcove at the start of level 10 near the pressure plate.
moo5003 wrote:You should have already found it to get through an iron gate. Assuming you didn't pick it back up it will be in an alcove at the start of level 10 near the pressure plate.
Duh. Thanks.
I just found out I can cut the curtains.