The "Key" comb. My observations

I have opened up a lot of honey bee nests in the process of doing my job as a pest control technician who works to keep bees alive.  My specialization, as it were.

I have found honey bee nests in some interesting places and in a lot of common places.  Soffits, roofs, ceilings, walls, underneath floors and in the rafters.  I have found them in mailboxes, under decks, in trees, in vehicles and lots of other places.

One consistent thing I find in all of these honey bee nests is that they have a "Key" comb.  That is, one comb that the bees started drawing before any other comb.

In most nests, adjacent combs are built parallel to this central, "Key" comb, using it as a guide to make those immediately next to it.  They then draw combs outward in both directions from there, using te previous drawn combs as guides for the next.

The bees don't necessarily have to have the "Key" comb fully drawn out to full size before starting on the next ones.  They often get the key comb about one fourth to one third drawn when they start drawing out the adjacent combs and sometimes even sooner than that.

Key combs are extremely important in any new nest site because not only are they used as a guide for other combs, but it is usually the comb that the queen begins to lay new eggs in first.  Also, new forage such as pollen and nectar are stored on that comb and the ones drawn out on either side as soon as they are made.

If the bees cannot draw comb right away, they are in BIG trouble.

In a managed hive, I prefer to start my new colonies with a central "Key" comb as well.   By placing a frame of already drawn comb or a sheet of foundation in the #3 frame (I use 5 frame boxes for my vertical hives so #3 spot is the very middle or center location.)  Even just using a sheet of foundation can be a tremendous help for the bees as the new comb they draw is to draw out the cells already imprinted instead of starting from nothing.  It's not critical, but helpful.

Personally, I use foundation-less frames in frame locations 1-2 and 4-5.  I do use guide strips in the upper groove of the frame to hopefully help the bees to draw straight combs.  Between the "Key" comb and the guide strips, they usually do pretty well.

I prefer to have the bees draw as much comb for themselves as possible to ensure the cleanest comb to lay eggs in and minimize transference of disease and pests between hives.  Though, as I mentioned, I will use a sheet of foundation for the "Key" comb as it helps the bees to a quicker, more efficient start than having nothing.