Franklin uses the manufacture of a knife as a metaphor for the importance of underlying quality. However skilfully a blade is shaped or sharpened, defective steel limits what can ultimately be produced from it. Applied more broadly, the saying suggests that durable excellence depends on sound foundations rather than appearance or finishing alone.

When applied to people, the comparison is best understood as a statement about character and habits rather than an unchangeable judgement about innate worth. Qualities such as integrity, discipline and judgement provide a foundation on which abilities and achievements can be developed. Unlike steel, however, people can learn and change. Franklin’s broader point is that outward accomplishment cannot reliably compensate for serious weaknesses in the qualities supporting it. Attention to the underlying material, whether literal or figurative, is therefore essential to producing something dependable.