The natural lines that appear in lumber are known as wood grain. These lines are created by the sawing pattern used when the mill first cuts the boards in relation to the angle of the growth rings. Each tree species and year of growth creates a unique and consistent ring pattern, much like a fingerprint. Wood grain is not only important for aesthetic purposes, but it also affects how a board dries and absorbs finishing stains.

To manipulate the grain of boards, saw mills pay close attention to the direction in which a log is cut. The most common method is quarter sawing, which creates parallel plains and consistent grain lines along the length of the board. Flat sawing is another popular method, but it produces unappealing grain patterns and is typically used for internal construction. Sawing methods such as rift or radial are often used for finishing wood and veneers, as they provide greater control over the grain direction, resulting in a more beautiful finished product.