This afternoon, I went to my welding supply to exchange a tank of oxygen. The guy in front of me was telling the guy at the counter that he was a welder for an aerospace company. He said that every frame they built wether it was chrome moly or aluminum they welded on two female pipe bungs. One was for an air gauge and one was for an air chuck. After they welded the frame they attached the gauge and air chuck and pressurized the frame. If the air gauge went down they new that had an incomplete weld or a pin hole. I never heard such a thing.