Grade А

All four sides are clean, without decay.

Grade AA/AB

Small live knots up to 12 mm in diameter are allowed, one piece per one linear meter of the board. Presence of two uprights 120*2200 mm.

Grade В

One side is clean and 4 sides adjacent to it are 50% clean. Used for the manufacture of surfaces of tables, stairs, chairs, etc.

Grade С

Small live knots up to 60 mm, up to four pieces per linear meter, and black knots up to 30 mm, up to two pieces per linear meter.