Lumber is susceptible to several common defects. These can occur naturally (such as knots) or during sawing, stacking or drying processes.
![](http://toolnotes.com/wp-content/uploads/2022/03/Wood-Defects-and-Warpage-1-1024x463.png)
Bow
Bowing is curvature along the length of the wide face of the board. A bowed board will rock longitudinally when placed on a flat surface.
![](http://toolnotes.com/wp-content/uploads/2022/03/Bow.png)
Cup
Cupping is curvature across the width of the wide face of the board.
![](http://toolnotes.com/wp-content/uploads/2022/03/Cup.png)
Crook or Crown
A crook (also called crown) occurs is curvature along the length of the narrow face or edge of the board.
![](http://toolnotes.com/wp-content/uploads/2022/03/Crook.png)
Twist
Twisting is a deviation from parallelism of the end edges of the board. A twisted board is curved along its own axis.
![](http://toolnotes.com/wp-content/uploads/2022/03/Twist.png)
Wane
Wane occurs when a board is sawn near the outer periphery of a log. There is not enough wood present in the location of the cut to completely fill the outer dimensions of the bard.
![](http://toolnotes.com/wp-content/uploads/2022/03/Wane.png)
Knot
Knots occur where a tree branch is overgrown by a tree trunk. Sound knots (knots that are firmly in place) my not be considered defects in certain species and applications.
![](http://toolnotes.com/wp-content/uploads/2022/03/knot.png)
Knot Hole
A knot hole is a void left where a dead knot has fallen out of its position in the board or tree.
![](http://toolnotes.com/wp-content/uploads/2022/03/Knot-Hole.png)
Check
Checking occurs along the radially across the growth rings of a board. Checks do not extend completely through the board.
![](http://toolnotes.com/wp-content/uploads/2022/03/Check.png)
Shake
Shakes are separation of growth rings.
![](http://toolnotes.com/wp-content/uploads/2022/03/Shake1.png)
Split
Splits are cracks in a piece of lumber that extend completely through the board.
![](http://toolnotes.com/wp-content/uploads/2022/03/Split.png)
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