Apparatus for determining the thickness of a configuration having flat, parallel surfaces that are transparent, or nearly so, to pre-specified types of energy. The mud gun cap includes a flame resistant outer face, a ring and a mounting device wherein the mud gun cap connects to a mud gun nozzle to protect the mud gun nozzle from deterioration because of contact with molten iron and slag. Also, another via to be electrically coupled to the third wiring as the word line is directly coupled to a contact plug electrically coupled to the gate wiring part of another access transistor.