Hi Van
There is the potential here for some confusion. The Mann-Lake graphic of their board shows it as being a Snelgrove Board with a
divided screen. So - is this a 'double-screen board' which actually has a single-
sided screen ? That needs checking (imo).
If you search around for info on Snelgrove Boards, you'll find that some have large area screens (such as Mann-Lake's), and some have only a 4"x4" screen in the centre. But - far more important - is that some Snelgrove Board plans on the Internet are being shown as having a
single-sided screen, but some have
double-sided screens - and of course there is a world of difference between them.
For the benefit of any beginners who may be reading this, the different lies in the ability of bees to contact each other. With a double-sided screen, the bees cannot make direct contact with each other (which is a necessary precaution if there are queens on either side of the board), and so they cannot engage in trophylaxis (the sharing of food and the passing of contact pheromones), although warmth and volatile pheromones will still pass through. Whereas with a single-sided screen, there is almost full contact - it's just that the bees cannot actually mingle together, and thus fight. That is, until they are allowed to mix, once they have become used to each other's smell.
So - single-sided screens are best when your intention is to combine two colonies, but use double-sided screens if you intend to keep two queen-right colonies apart, but just allow the upper colony to benefit from warmth passing up from below.
Van - you may find the following .pdf (concerned with re-queening without de-queening first) useful:
http://www.tandfonline.com/doi/pdf/10.1080/00288233.1972.10421270They don't specify what type of division board they used - I suspect either un-screened or one fitted with a queen-excluder (they don't say), as they used newspaper to provide temporary separation - but you may form one or two ideas of your own from reading it.
'best
LJ