Thank you Philip, for your response to my question. I noticed, in comment #11 in this thread, that you said, "I like it because with clear crownboards with a rim I can see the bees walking around on top of the frames when I peer in and that gives me pleasure..... "
Can you please clarify something for me? The concept of TBS - Top Bee Space - seems to be very popular. It seems to me, that if a hive body is constructed to provide 8mm TBS, then the top of a frame will be 8mm below the level of the top of the hive box. In other words, any plain sheet of material, whether it be plywood, perspex or polycarbonate, when placed directly onto the box will have 8mm clearance between it and the top of the frames. If this is the case, then why would it be necessary to enclose a plastic sheet in a wooden frame to create an additional 8mm clearance?