The buckler was a small round or rectangular shield, measuring from 6-18 inches in diameter, and was used to deflect an opponent's blows and protect the wielder's sword hand.
The buckler was a very small shield. As such, it was ineffectual in blocking missiles. However, it was perfect for deflecting, not blocking, opponent's weapons. It could also be used to hide the wielder's sword hand from view, giving the wielder a split-second advantage, as their opponent would be left guessing as to what strike is coming. The buckler could also be used as a type of metal fist, to punch at the opponent with it as an improvised weapon of attack. Finally, the buckler could be used to grapple the opponent's sword and shield, a distinct part of late medieval swordplay.