Hamming, two paragraphs after the welding example: in any design, field maintenance must be considered from the start, because in the long run it often dominates all other costs. The more complex the system, the more central it must be. And it cannot be safely grafted on later.
In software this is the argument for observability, migration paths, rollback, and seams being designed alongside the feature rather than after it.
Note the tension with his own illustration: Welds trade serviceability for production cost
Source: The Art of Doing Science and Engineering: Learning to Learn