A part came with my RM100C and I don't know why.

There's a part that came with my amp and I can't figure out what the purpose of it is.

This is the amp with all pieces of the back of the cabinet removed.


Here is is with the bottom piece (I left out the screws but you get the idea):


Here it is with the top piece:


Now here is the piece that I can't figure out. There are no screw holes or anything to mount it with. This was in the box with the amp and it appears to be made out of the same material as the amp:


Here's a little bit of a wider angle shot.


So I see that there is a little bit of a gap between the amp chassis and the back of the cabinet:


So I wondered if it was meant to go there. I tried it turned both upright and flat and it fits snuggly when I lay it flat in the second picture, but it still seems kind of weird to me:

Upright (it fits loosely but seems stupid because it covers up the ports on the back of the amp.. this can't be right)


Flat (fits snug but just seems weird.. I thought maybe it was meant to totally seal the cabinet, but it still seems odd that it doesn't actually have holes for screws/bolts):


I looked in the manual and didn't see anything about it and after a few quick forum searches no one else asked about it. I'm sure it's something totally obvious and I just can't see it. Can anybody help the slow guy?

Thanks,
John

When you make it a 3/4 open or full open screw the extra board in place to protect the tubes.

Screw it in what place? Do I just have to guess and then drill new holes for it or is there an exact place that randall had in mind when they decided to include the board? I wonder why they didn't bother to pre-drill the holes in the extra board?