What is the grade of wood

The grades of wood are A AB ABC B BC C as follows:

A: No stutter, no mineral wire, no tree core, no decay, no bending, no end cracks, simply no flaws

AB: No stutter on one side, no mineral thread; but no tree core, decay on both sides, may have partial bending and end cracks

ABC: This level is easy to summarize, that is, all the boards processed from the whole log. Of course, the log will have fewer defects, mainly because it lacks a selection process.

B: There are stutters on both sides, there are mineral lines, bends, end cracks, but no tree core, no decay

BC: There are stutters on both sides, mineral lines, bends, and end splits account for half, and tree cores account for half, no decay

C: core material, the ends may be partially decayed

The above are domestic and European standards