The position of the top lever generally indicates the amount of wear on the bolting surfaces of the gun. If the gun has underbolts ala Purdey the wear is indicated on either the lump slots or the bolting wedge. A rotary bolted gun ala L.C. Smith, A.H. Fox, Ithaca, etc., the position generally indicated the wear either on the rib extension slot or the radius of the rotary bolt. This method is not foolproof but a good guideline to indicate wear on such surfaces. Chopperlump