Never split timber against the grain.

The saying advises working with a material’s inherent structure rather than forcing it in a direction that resists it. In practical terms, splitting wood along its fibres is easier, cleaner, and less wasteful than trying to break across them.

Figuratively, it recommends recognizing the natural tendencies, limits, or established conditions of a task before acting. It cautions that effort spent fighting those conditions may produce needless difficulty, while an approach aligned with them is more likely to succeed.

Use it as practical or figurative advice when someone is choosing a method that ignores the way a material, process, or situation naturally works. It can encourage adaptation and sound judgment, rather than stubbornly forcing an unsuitable approach.