Blood groove? Where?
Here’s what I learned after someone else learned.
These grooves are often called “blood grooves” or “blood gutters” as well as fullers, although their purpose has nothing to do with blood. A fuller is often used to lighten the blade, much the way that the shape of an I-beam allows a given amount of strength to be achieved with less material.
… learn something new every day! So I don’t think they are visible per say.