To provide an inspection method by which condition of a pressure side wall and/or a suction side wall is visually determined.

A casting includes a wall thickness check feature for measuring thickness of a wall at the side of an in-wall cooling passageway. The thickness is determined by observing the existence and/or size of an opening formed by the feature. The casting is cast from a pattern including portions forming the feature. To manufacture the pattern, a pattern-forming die is assembled with a ceramic feedcore and a refractory metal core (RMC). The assembling leaves an inlet portion of the RMC engaged to the ceramic feedcore and leaves an outlet portion of the RMC engaged to the die. A pattern-forming material is molded in the die at least partially over the ceramic feedcore and RMC. The die is disengaged from the pattern-forming material. The assembling engages a stepped projection of the RMC with a mating surface of the die.