scan

 ... here's a cool scan ... shows No. 1 Grade lumber (in this case DF-L) of different widths and knot sizes. 

For our purposes ... Species or Species Group lumber are sorted into Stress Grades.

The most apparent factor in Stress Grades are `knots'. 

Knots are considered a strength reducing characteristic.  Thus, within each Grade there are limits on knot sizes.

We'll talk more about this in class.

Scan is from the WWPA literature (Western Wood Products Association).

NOTE: as a designer you will generally NOT be `grading' wood products ... but you will be SPECIFYING wood products. 

(So this is what they look like! ...)
Grading of wood products is done by people who are trained and certified to do so.

On occasion I need to make a `field judgement' (opinion) on a certain grade of lumber ... stuff like this (above) helps.

Doc