Speaking of the shield bosses, Byzantine military treatises apparently at one time recommended giving the front rank of an infantry formation spiky ones and the men behind them "flat" ones. The idea obviously being that in a close shieldwall push the spiky front ranks would be that much nastier for the enemy, while the rear ranks could still use their shields to physically push their comrades forward (the ancient hoplites apparently used the same approach).

This sort of creative mix-and-match approach seems to have been fairly typical of the lot.