Back-step welding involves depositing short adjacent weld lengths in the opposite direction to the general progression (Fig.1a).
Skip welding is laying short weld lengths in a predetermined, evenly spaced, sequence along the seam (Fig.1b). Weld lengths and the spaces between them are generally equal to the natural run-out length of one electrode. The direction of deposit for each electrode is the same, but it is not necessary for the welding direction to be opposite to the direction of general progression.
For more information on the control of distortion, see Job Knowledge for Welders 36.