It shows rings, rays, and cells. R is a radial view of the wood. It shows the rings in side view. They appear as vertical streaks. Radially cut or quarter-sawn wood is expensive because only a few pieces can be obtained from each log.
T refers to a tangential cut.
It shows the ends of the rays. Annual rings appear as irregular bands of light and dark streaks or patches. This is the most common cut. Knots are the bases of lost branches which have been covered in time by new annual rings. Lumbering and Milling Wood must be seasoned or dried in the open air, in kilns , or with fans.