Piece fallen off my printer near the roller

[B17Fan]

i had a Paper Jam a few weeks back. Didn't look up how to fix it, I instead took the printer apart from the top. I took this piece off and put it back where i thought it went, but everytime i print now, it falls down and comes out if I pull the paper tray out. 

Can someone tell me where if goes and how to put it back please?

[Valsimot]

[Hapone1]

I think it seems to fit under here, as it seems to fit around the wheels. But it keeps falling through when i print, or i get a paper jam. How can i secure it?

photos are in reverse order, Just how it's all put together when you look in there 

[Valsimot]

You need to place it under that paper feed shaft with black round parts, you need to remove the shaft, place the part that came off and then put the shaft back.