The jaws are the part of the tool in front of the pivot bolt (see below). They are used to grip and cut the steel wire ties that hold rebar together for steel reinforced concrete.
The cutting edges are ground onto the tips of the jaws. Cutting edges can be applied to both jaws as in a double sharp design or can have a knife and anvil design.
Concretor’s nippers with a knife and anvil cutting edge design have a sharp cutting edge applied to the upper jaw and a flat anvil surface applied to the lower jaw. The manufacturers of this design claim it extends the working life of the cutting edge.