A cutter assembly (120) may include a knife guard holder (24) to be removably connected to a cutter bar, a knife guard (26), and an interface (130) between the knife guard holder (24) and the knife guard (26). The knife guard (26) may have a knife channel (44) to slidably guide a cutter knife. The interface (130) extends between the knife guard holder (24) and the knife guard (26) to locate and releasably retain the knife guard (26) with respect to the knife guard holder (24).