Lumber Grades At A Glance

Domestic hardwood lumber found at sawmills meets different quality levels or grades as specified by the National Hardwood Lumber Association (NHLA). The basis for this wood grading is the number and size of defect-free clear cuttings in a board, as summarized below, Thickness is not a consideration, though with some species worm holes, gum pockets, and stain are acceptable.
FAS (First & Seconds) lumber grade. This premium grade represents the finest lumber yield in a log. Generally, the minimum size board is 6" wide by 8' long which yields a minimum of 83 1/3% clear cuttings on its poorest face.
F1F (FAS One Face) lumber grade. The best face grades as clear FAS; the worst, as #1 common, containing some knots.
Selects lumber grade. Close to a FAS board. A Select board must be a minimum of 4" wide and 6' long and yield a minimum of 83 1/3% clear cuttings, but only on one face with #1 common on the worst face.

#1 Common. An economical choice for wood furniture that requires moderate lengths and narrower widths. A #1 board must be a minimum of 3" wide and 4' long and yield 66 2/3% clear cuttings on the worst face. Expect some mineral streaks, splitting, wane, knots, and tool marks in wood(in rough-sawn).
#2 Common lumber grade. This grade allows many defects, including sound and unsound knots, pith (the unstable center), shakes (splits between growth rings), tool marks, wane, and checks (splits), if they don't affect strength. Minimum board size: 3" wide and 4' long. Each board must yield a minimum 50% usable, but not defect-free wood.
#3 Common. Not suitable for woodworking due to number of defects and low yield of usable wood.

Grade Name	Abbreviation	Minimum Board Size	Usable Material on One Face
First and Seconds	FAS	6-in. x 8 in.	83%
Select	Sel	4-in. x 6 in.	83%
#1 Common	#1 Com	3-in. x 4-in.	66%
#2 Common	#2 Com	3-in. x 4-in.	50%

Grade Stamp

1. Manufacturer: Mill's number, name or symbol. (ex. 12)
2. Certification mark: Symbol of agency providing quality control supervision. (ex. WWP®) 
3. Grade: Often abbreviated. 1 Common shown. (ex. 1COM)
4. Moisture content (MC): Abbreviations for MC when board surfaced: MC 15 is 15 percent or less; KD or S-DRY is 19 percent or less; S-GRN is green wood with more than 19 percent MC. (Ex. S-DRY) 
5. Species mark: Symbol or abbreviation for types of tree.