This knife mounts on the left side of the mower disc to sever the crop during cutting. It is the replaceable wear component that contacts the crop directly; the cutting edge engages the standing forage and transfers the impact load to the disc assembly. A dull or chipped knife reduces cut quality and increases power draw on the driveline. The manufacturer machines this replacement to the same hole spacing and thickness as the original so it seats flush against the disc face without shimming. When installing, use the specified fastener torque and check that the knife rotates freely on its mounting bolt before operation.