Weld run-off/run-on area
The design extension of the weld beyond the actual component edge using run-on and run-off tabs. This prevents porosity and crater cracks at the actual component boundary.
The run-off tab is the piece of weld that you lead beyond the end of the workpiece onto an auxiliary piece. This moves the weld crater, i.e., the end point of the weld, away from the actual workpiece, because that's exactly where pores or cracks tend to form. You draw the molten pool cleanly onto the run-off tab and let the arc die out slowly there instead of breaking it off abruptly – this prevents crater cracks at the end of the weld. The run-off tab must be big enough that the entire pool fits on it, otherwise it will run off the back. After that, you just grind or break the piece off.