I have noted recent discussion about comb building between the tops of
frames and the inner cover.  The Dadant inner covers come with what I think
could be better  instructions. Of the four reasonably possible ways to
build and install the covers, three are wrong: the *shallow* side of the
cover with the smooth side of the masonite needs to be down, facing the
tops of the frames. Someone named Experience came along to teach me that.
If the "deeper" side of the Dadant inner cover faces the tops of the
frames, there is a 15 mm space for bees to build comb you do not want.
Cal French, Central Coast of California