The “Bee-Space” is the gap which bees will leave clear as a passageway between the frames and the hive walls, and it is most important because without it we could not remove and replace frames as we do.
The bee-space is 1/4 -3/8 in (6-9mm); a smaller gap would be filled by the bees with propolis (bee-glue) and they would build extra comb in a larger one. Basic Hive components allow variation in the dimensions of different hives and in the provision of top or bottom bee-space.
A bee-space must also exist between brood boxes and supers; otherwise they would be difficult to separate. Traditionally the British elected to have bottom bee-space, so that the tops of the frames were flush with the top edges of the box but the bottom bars were in (9mm) short of the lower edges.