Edge Versus Flat: What to use for parrying?

A techniques video is overdue! A few years back I did separate videos about using the edge and the flat but this one is a combined look at why both work, and how they work. I suppose it's an update on my thoughts as I progress in the area of both learning and teaching historical martial arts. Thus, I compare the edge to the flat and discuss when to use each of them in parrying that incoming attack!