I cut T-shaped follower boards out of some old boards I had to narrow-up two of my deeps that had an undersized colony it, which I was advised to transfer to a stacked double nuc box for the winter. It was late in the my first summer and I was sort of sick of buying new stuff for the bees by then.

I have two follower boards in each brood box, and after I had lightly re-arranged the frames so I had a matching vertical column in both the boxes, I moved the follower boards inward until they were a side-of-hive-space away from the edge of the frames and made sure they matched in both boxes. Then I filled the cavities outside the follower boards with T-shaped pieces of foam insulation to snugly fill up the vacant space between the follower boards and the hive's sides. The follower boards and the foam pieces rest on the rebate that normally supports the frames and they also stick up to be flush with the top edge of the boxes.

(I have since read that bees may chew on foam insulation, but I haven't seen that so far. I am watching for it very carefuly and if I use this in other years I will take steps ahead of time to cover the foam so the bees can't get at it.)

Anyway, the key point is to make sure your follower boards, and any space-occupying insulation panels( if that's what you're about) are exactly the depth of the box so a stack of them forms one continuous vertical wall from top to bottom, with no horizontal bee-access under them like there is for frames. For the connection to the bottom board if you were running two colonies within the same box, I think I might add a bracket to hold a piece cut to rise up from the base and meet the follower board to securely separate the colonies from top to bottom. That's not an issue for me as only one colony lives in well-insulated comfort in the middle of my temporary double-nuc set-up.

In the sping I know I'll have to look lively and make sure to expand the space for the bees to avoid them swarming, but I expect it's the same with nucs, right? And in my case it can be a gradual, not an all or nothing, thing as I can extract some, but not all of the insulation to add enough space to put in one or two additional frames as needed. I'll just need to make sure both stories get expanded horzontally at the same rate, or I will lose the advantage of wood followers touching each other in the middle.

Bear in mind that this is my first attempt at this, and my bees, though alive today ,are not through their first winter. But so far, at least, I am happy with my idea, partiicularly since it uses all my other on-hand equipment: bases, quilt box, shims, feeders, etc. As much pleasure as it is to buy or make new woodenware, eventually ones just feels, enough!