ploughshare(n = noun.artifact) plowshare, share - a sharp steel wedge that cuts loose the top layer of soil;
is a kind of wedge
is a part of moldboard plow, mouldboard plough

   The share of a plow, or that part which cuts the slice of earth or sod at the bottom of the furrow. [1913 Webster]

ploughshare, n. the cutting blade of a plough.