I have a bit of a newbee question, I have seen this woodenware in photos (OMIE's was about the clearest to edit down to ask...) but wasn't familiar with its function. What is this box between the bottom board and the brood deep? Size-wise, It looks like a pollen trap but having read OMIE's posts, I didn't see any reference to one. (BTW: Thank you OMIE for the unauthorized use of your photo. Apologies in advance.) Curious?