The position and direction of the wood cells and vessels in relation to one another, along with the growth rings produce the grain, a fundamental visual feature of the different woods.

The groove is the channel made with a mortiser into the wooden board. The groove fits together with the tongue of the corresponding board to form a join.

When a perpendicular cut is made to the stem axis, aside from the bark, you can also identify the xylem, which is formed from the cells which grow each year (earlywood and latewood). Using the growth rings, it is easy to identify the boundaries of these growth areas.

The width of the growth rings and the ratios of early and latewood depend on endogenous (genetics, physiology) and exogenous factors, such as the soil conditions of the location and climatic conditions. The width of growth rings ranges between 1 and 10 mm, and there can also be variations within one trunk.