Text equivalent
Cup
Curvature across a board’s width.
Bow
Curvature along the face length.
Crook
Curvature along an edge.
Twist
Corners depart from one plane.
Describe direction and location before discussing cause. These vocabulary distinctions do not grade a board or establish safe use.
Download diagram (SVG)Original educational diagram · Hardwood Failures · September 14, 2026.