throat

A timber knee is a naturally curved piece of wood, or an artificially bent timber, used to brace two members meeting at an angle, typically where a beam joins a post or where a deck beam meets a ship's side. The throat is the inside corner of this L-shaped or curved member, the acute angle where the two arms of the knee meet. In structural terms, it is the most stressed region of the knee under load.

The throat determines both the strength and the workability of the knee. A sharp throat, with a tight radius of curvature, concentrates stress and can cause failure by splitting or crushing along the grain. A generous throat with a broad radius of curvature distributes stress more evenly and resists fracture better, but requires more material and labor to shape. Shipwrights and timber framers must balance these demands. Knees cut from the natural crook of a tree have throats formed by the tree's own growth pattern and are stronger than those made by bending or sawing, because the grain flows through the throat rather than being cut across it.

Iron or steel knees, forged or cast for heavy industrial and maritime work, have throats designed with generous radii and sometimes reinforced with additional metal or ribbing at the throat to prevent cracking under dynamic loads. Timber knees in shipbuilding are installed with the throat pointing inward, toward the junction being reinforced, so the wood grain can more effectively resist the shear and compression forces that develop there during flexing and impact.

Defects at the throat are a primary reason for knee failure. Checks (splits), knots, and grain run-out at the throat weaken the joint catastrophically. Carpenters inspect knees carefully at this point and reject or reinforce any showing visible damage. The throat is also where seasoning cracks most often initiate in timber knees, because the sharp angle concentrates moisture gradients and shrinkage stress.

The term throat appears elsewhere in timber framing to describe other tight angles, but in the context of knees it refers specifically to this load-bearing interior corner. Understanding the throat's role is essential for anyone selecting, fabricating, or installing braces in timber-frame structures.