Which of the following welding positions is NOT possible according to the second to last digit of the electrode?

The choice indicating vertical fillet welds only is not correct with regard to the welding positions allowed according to the American Welding Society (AWS) classification system which uses the second to last digit of the electrode designation. This digit specifies the welding positions in which the electrode can be used effectively.

Electrodes classified with a '1' as the second to last digit can be utilized in all positions, which includes flat, horizontal, vertical, and overhead positions. When the digit is a '2', this indicates that the electrode is suitable for flat and horizontal positions only, but not for vertical welding. Since the question pertains specifically to the vertical position and its limitations, it stands that vertical fillet welds, which require the ability to weld in a vertical orientation, would not be possible for certain electrodes based on the specified classification system.

Therefore, the answer provided aligns with the understanding that not all electrodes can be used for vertical fillet welds. The choice correctly reflects the restrictions placed on electrode usage concerning welding positions and guides welders in their practices according to the AWS standards.