Crook (Lumber Defect)
Crook is a warp defect where the board curves along its edge from end to end, sometimes called crown. Unlike bow which curves along the face, crook curves along the narrow dimension. It is measured by the deviation from a straight line along the edge.
In-Depth Explanation
Crook — also commonly called crown in framing terminology — is a lateral bend in a board visible when sighting down the edge. It results from differential shrinkage across the width of the board, reaction wood from leaning trees, or grain that spirals around the tree. In framing construction, slight crook in studs and joists is normal and often manageable. Framers typically install studs with a consistent crown direction so walls remain plumb. Severe crook in finish lumber is harder to correct because ripping the board to straighten it significantly reduces width. Proper stacking and stickering during drying minimizes crook development.
Usage Example
When framing the wall, the carpenter sighted down each stud to identify the crook and marked the crown side so all studs bowed in the same direction.