Grimrock

Seems I'm stuck on level 4 and can see the stairs but there is a gate/grate blocking the way - near the iron door on level 4. I've gotten the key to the Iron Door on that level and opened it (hoping that would be the ticket..but alas that wasn't it). So now stuck going around in circles and banging the head as to how to get to the other side of that grate. Hint?

No idea how big hint you want. =) In general, you should solve the puzzle involving wall signs in room before the grate, niches in pillars there, and scrolls found on the sublevel.

I thought it was pretty obvious :9 A lot bigger problem is the book in Time & Tide for me :/