Which welding position refers to a vertical weld made from the bottom upwards?

The vertical position is correctly identified as the welding position where the weld is made in a vertical plane and progresses from the bottom upward. This position is commonly encountered in various structural applications, particularly when dealing with beams and columns, where a vertical weld might be necessary to join two pieces of metal or to reinforce a structure.

In the context of the AWS D1.1 Structural Welding Code, understanding the different welding positions is crucial as each position presents unique challenges and requirements for techniques and equipment settings. The vertical position allows for specific types of welding procedures, such as stringer beads or weaving techniques, which can influence the weld quality and penetration.

Each of the other options represents different welding positions. The flat position is for welds made on a horizontal surface, the overhead position is for welds made above the welder's head, and the horizontal position is for welds made along a level plane but with the weld face running horizontally. While all of these positions are significant in their own rights, they do not specifically denote the act of making a vertical weld from the bottom upwards, which is distinctly classified as the vertical position.