Stuck on level 3

[timelord]

I am trying to get the second key at the sacrificial puzzle, but there is a gate blocking the trap door that I am supposed to put something to sacrifice on. I know I'm missing something easy here, but I don't know what it is. Can anyone help this frustrated gamer?

[Merethif]

You can put item through gate. Don't throw the item though, just put it on a floor.