The natural wood grain is the term used to describe the lines that run through wood, created by the growth rings of the tree. The growth rings, which form annually as the tree grows, vary in thickness due to changing conditions. The orientation of the grain in a board is mainly determined by the way the tree was cut at the mill.

One method of cutting logs is quarter-sawing, which results in parallel planes of wood. Another method, rift sawing, involves cutting the log at radial angles, but this is less common due to the higher potential for waste. However, it produces the most stable pieces of wood with the straightest grain lines, as it is cut perpendicular to the growth rings. Flat sawing, the most common method, is efficient and produces little to no waste, but the grain patterns are generally considered less desirable for certain projects.