Just thought I'd mention an observation, not an uncommon experience, but interesting.
In order to have a better saturation of my mating area with drones of my preferred genetics, I cut a full, deep, sheet of beeswax drone foundation, in half -- then wired each half into its own medium frame. Within one day of having placed it on my strongest colony, the foundation part had been drawn out. I then placed both of them into the colony whose drones I wished to propagate. Once in the "drone builder" colony, the bees there continued to build comb on the bottom edge, to fill out the frame. One frame they quickly transitioned into small cell worker comb, the other they continued as drone comb. They always seem to know just what they want.