The root pass is welded with a "drag" technique. The tip of the electrode
is held in contact with both pipes and dragged around the circumference
of the pipe, progressing vertically downhard. The electrode initially
should be held roughly perpendicular to the pipe. If there is a
proper fit-up and the proper current is used, a small "keyhole" will be seen following behind the electrode. If the keyhole is not seen, the
electrode is not penetrating through to the inside of the pipe.