This is where the oil channel plug should be, but Stihl does not offer it as a spare part. In the event that this element falls out, the manufacturer recommends screwing a screw into this hole (not too deep so as not to block the transverse channel that goes to the guide), catalog number 00009531001, it fits tightly, so it is worth slightly warming the body in this place so that it does not break. You can also blind it with anything, but watch out for this transverse channel.
