Rule 14 of 31 · Chapter III — Read the Wood
Inspect boards for defects first
Why this rule exists
That gorgeous board might hide a knot where you need a joint, a check running deeper than it looks, or a cup that'll fight you all day. Case-harden internal stress and a board can pinch your blade or spring into a banana the moment you rip it. Looking a board over before you commit lets you cut around trouble and place the pretty grain where it shows, instead of discovering the flaw only after you've already invested the cut.
In practice
Sight down each board for cup, bow, twist, and crook before buying and again before cutting into it. Look carefully for loose knots, splits, checks at the ends, sapwood, and pith running through. Chalk out the defects you find and plan your parts around them, saving clear stock for the visible faces. Rip a suspect board a hair oversize and watch whether it moves or pinches, which reveals internal tension before it ruins a final, committed cut.
When it doesn't apply
Rustic and character work wants the knots, checks, and color streaks that furniture grade rejects, so inspect to feature defects rather than avoid them. And structural framing hidden in a wall forgives cosmetic flaws entirely. Match your scrutiny to whether the wood will be seen and whether the flaw affects strength.