Menuki - Hilt Ornaments
The menuki were originally used to cover the mekugi, the bamboo pins that
are keeping the tsuka (handle) on the sword's tang ,and prevent it from slipping
out.
Later on the menukibecame purely ornamenta and were placed about one hands
width from the fuchi (collar) ,on the outward side (Omote) and the kashira
(pommel) on the ura side of the sword that is facing the body (Ura) on a Tachi.
These days, the benefit of the menuki is to create a better grip on the tsuka
since the menuki are filling the gap in the palm of the hand.