Ezekiel 40:12

‘And there was a barrier in front of the side rooms, one cubit on this side and one cubit on that side. And the guard rooms were six cubits on this side and six cubits on that side.'

Detail is given of the guard rooms in order to draw attention to their importance, and to demonstrate their symmetrical perfection. They would, without any question, fulfil their functions. They had to be six cubits so as to make up the twenty five cubits across (five squared) when taken with the thirteen cubit wide corridor.