Hi @busso, what a tangled web we weave with these “simple” discussions.
The main problem is that hive builders in the US do not have an engineering mentality. Tolerances are wide. Totally unacceptable, I know, but true. It just has to work, it doesn’t have to be a perfect fit. That disappointed me hugely when I built my first US hives from flat-packed parts. I just had to school myself into the thinking that these are “agricultural” specs, not fine furniture. I still have trouble accepting that, but I am working on it.
Langstroth hives in the 8 frame size can be anywhere from 13.5" to 14" wide in the narrow dimension of the boxes. If you buy from 2 different suppliers, one could be cutting to 13.5" and the other to 14". Most cut at the smaller end of the range, because it uses slightly less wood. Flow decided to go with 14".
So If I mix boxes from Flow and others, I may have a 1/8 to 1/4" overhang on each side of the boxes. It doesn’t matter. They still seal well enough for the bees. They look fine from 20 feet away. But in my head, I know they are not aligned. That is my problem. OCD all the way. I have to learn to live with it, but thankfully the bees don’t care.